#+title: Emacs setup for use with LaTeX, Lisp, Org, and Python
#+author: Gerard Vermeulen
#+latex_class: article
#+latex_class_options: [11pt,a4paper,english,svgnames]
#+macro: kbd (eval (by-backend-kbd-org-macro $1))
#+options: ^:{} timestamp:nil
#+property: header-args:emacs-lisp :exports code :tangle init.el
#+startup: showeverything
#+begin_src latex :noweb yes :results raw
,#+latex_header: <<latex-header-1>>
,#+latex_header: <<latex-header-2>>
,#+latex_header: <<latex-header-3>>
,#+latex_header: <<latex-header-4>>
,#+latex_header: <<latex-header-5>>
#+end_src

* Copying
:PROPERTIES:
:CUSTOM_ID: sec:copying
:END:

This README contains my Emacs setup for use with LaTeX, Lisp, Org, and Python.
Copyright \copy 2021-2024 Gerard Vermeulen.

#+BEGIN_QUOTE
All Org-mode source blocks with function definitions in this document are free
software: you can redistribute it and/or modify it under the terms of the GNU
General Public License as published by the Free Software Foundation, either
version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
#+END_QUOTE

#+BEGIN_QUOTE
Permission is granted to copy, distribute and/or modify the other parts
of this document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, with no Front-Cover Texts,
and with no Back-Cover Texts.  You should have received a copy of the GNU
Free Documentation License with the source file of this document. If not,
see <https://www.gnu.org/licenses/>.
#+END_QUOTE

* Quick start
:PROPERTIES:
:CUSTOM_ID: sec:quick-start
:END:

This setup requires at least Emacs-30.  The installation procedure starts with:
1. Backup the =user-emacs-directory= which defaults often to =~/.emacs.d=.
2. Run the listing [[lst:prepare-user-emacs-directory-with-https][prepare the =user-emacs-directory= without =ssh= access]] or
   the listing [[lst:prepare-user-emacs-directory-with-ssh][prepare the =user-emacs-directory= with =ssh= access]] commands.
After invoking Emacs interactively, Emacs will ask you to install a selected set
of packages.  Quit Emacs and invoke Emacs again.

#+caption[Prepare the user-emacs-directory without =ssh= access]:
#+caption: Clone and initialize the user-emacs-directory without =ssh= access.
#+name: lst:prepare-user-emacs-directory-with-https
#+begin_src shell -n :eval never :tangle no
cd ~
git clone https://forge.chapril.org/gav451/emacs.d.git .emacs.d
make --directory=.emacs.d init
emacs &
#+end_src

#+caption[Prepare the =user-emacs-directory= with =ssh= access]:
#+caption: Clone and initialize the user-emacs-directory with =ssh= access.
#+name: lst:prepare-user-emacs-directory-with-ssh
#+begin_src shell -n :eval never :tangle no
cd ~
git clone ssh://gitea@forge.chapril.org:222/gav451/emacs.d.git .emacs.d
make --directory=.emacs.d init
emacs &
#+end_src

* Introduction
:PROPERTIES:
:CUSTOM_ID: sec:introduction
:END:

This Emacs setup aims to install automatically a minimal set of extension
packages that allows to handle my reports and presentations.  The file format of
the reports is [[https://orgmode.org/][Org Mode]] plain text with [[https://www.python.org/][Python]] source code blocks and the file
format of the presentations is [[https://www.latex-project.org/][LaTeX]].

This [[info:org#Top][org]] file (more precisely the original [[info:org#Top][org]] source file of this file)
illustrates three methods in my work-flow:
1. How to tangle (or export) source blocks from [[info:org#Top][org]] files. This file contains
   source blocks to produce the files =early-init.el=, =init.el=, =latexmkrc=,
   =org-store-link=, and =example.py= by tangling.
2. How to export [[info:org#Top][org]] files to other formats such as [[https://en.wikipedia.org/wiki/HTML][HTML]], [[https://www.latex-project.org/][LaTeX]], and [[https://en.wikipedia.org/wiki/PDF][PDF]].
3. How [[info:org#Hyperlinks][org hyperlinks (info)]] allow to link inside and outside [[info:org#Top][Org Mode]]: hover
   over or click on the links to experiment.

The [[https://en.wikipedia.org/wiki/AUCTeX][AUCTeX - Aalborg University Center TeX]] extension package provides a
powerful [[https://en.wikipedia.org/wiki/Text-based_user_interface][Text-based User Interface (TUI)]] environment to edit the [[https://www.latex-project.org/][LaTeX]]
presentations.

The [[https://github.com/bdarcus/citar][Citar]] extension package provides quick filtering and selecting of
bibliographic entries, and the option to run different commands on those
selections.  [[https://github.com/bdarcus/citar][Citar]] exploits the extension packages [[https://github.com/minad/vertico][Vertico]], [[https://github.com/oantolin/embark][Embark]], [[https://github.com/minad/marginalia][Marginalia]],
and [[https://github.com/minad/consult][Consult]].  The [[https://github.com/andras-simonyi/citeproc-el][CiteProc]] extension package provides [[https://citationstyles.org/][CSL: citation style
language]] processing capabilities to [[https://github.com/bdarcus/citar][Citar]] and [[https://orgmode.org/][Org Mode]].  A curated repository
of CSL styles is the [[https://github.com/citation-style-language/styles#readme][citation style language repository]].

The [[https://github.com/vedang/pdf-tools][PDF-Tools]] extension package renders [[https://en.wikipedia.org/wiki/PDF][PDF]] file with the possibility to
annotate the file or to click on anchors in the [[https://en.wikipedia.org/wiki/PDF][PDF]] file that link back to the
original [[https://www.latex-project.org/][LaTeX]] file of the document.  An example of my work-flow are the steps
to convert this [[info:org#Top][org]] file to [[https://en.wikipedia.org/wiki/PDF][PDF]] and to see the result with [[HTTPS://github.com/vedang/pdf-tools][PDF-Tools]] in Emacs:
execute the commands ~pdf-tools-install~, ~org-babel-tangle~,
~org-latex-export-latex-to-latex~, and ~compile~.  This sets up an infinite
[[https://www.latex-project.org/][LaTeX]] compilation loop to update and redisplay the [[https://en.wikipedia.org/wiki/PDF][PDF]] file after execution of
the ~org-latex-export-latex-to-latex~ command in this buffer.

Here follows a list of links on how to use Emacs and Elisp:
1. [[https://www.masteringemacs.org/][Mastering Emacs]] is a link to a blog with interesting posts that promotes a
   book on how to become a proficient Emacs user.
2. [[https://www2.lib.uchicago.edu/keith/emacs/][Use GNU Emacs: The Plain Text Computing Environment]] explains the fundamentals
   of the Emacs abstractions before showing how to exploit those abstractions
   interactively.  It targets a similar audience as the [[https://www.masteringemacs.org/][Mastering Emacs]] book.
3. [[https://www.youtube.com/watch?v=lkIicfzPBys][A guided tour of Emacs]] is a link to a video tour pointing how [[info:emacs#Buffers][buffers (info)]],
   [[info:emacs#Dired][dired (info)]], [[info:emacs#Help][documentation (info)]], [[info:elisp#Top][elisp (info)]], [[info:elisp#Debugging][elisp debugging (info)]],
   [[info:eshell#Top][eshell (info)]], and [[info:emacs#Keyboard Macros][keyboard macros (info)]] turn Emacs in an powerful coding
   and editing environment.
4. [[https://www.youtube.com/watch?v=6ZWp05OW1c0][Emergency Emacs]] is a link to a video on fundamental editing features and
   principles with focus on [[info:ediff#Top][ediff (info)]], [[info:emacs#Undo][undo (info)]], [[info:emacs#Moving Point][moving point (info)]],
   [[info:emacs#Erasing][erasing (info)]], and [[info:emacs#Dynamic Abbrevs][dynamic abbreviations (info)]].
5. [[https://endlessparentheses.com/][Endless Parentheses]] is a blog with mindblowing code snippets.
6. [[https://www.murilopereira.com/how-to-open-a-file-in-emacs/][How to open a file in Emacs]] looks into [[info:elisp#Top][elisp (info)]] and
   [[info:elisp#Debugging][elisp debugging (info)]] and then compares Emacs, [[https://www.vim.org/][Vim]],
   [[https://neovim.io/][Neovim]], and [[https://code.visualstudio.com/][Visual Studio Code]] with respect to values and technology.
7. [[https://protesilaos.com/codelog/2022-01-31-learning-emacs/][Learning Emacs and Elisp]] is a link to a video tutorial with a transcript on
   the best approach to learn Emacs and Elisp.

* [[info:emacs#Early Init File][Early Init File (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:early-init-file
:END:

Try to load [[https://github.com/emacscollective/no-littering][no-littering]] as early as possible, since it helps to keep
=~/.emacs.d= clean.

#+caption[Tangle the early-init-file]:
#+caption: Tangle the early-init-file.
#+name: lst:tangle-early-init-file
#+begin_src emacs-lisp -n :results silent :tangle early-init.el
;;; early-init.el --- user early-init file        -*- lexical-binding: t -*-
;;; Commentary:
;;; Code:
(setq load-prefer-newer t)

(require 'no-littering nil 'noerror)

(provide 'early-init)
;; Emacs looks for "Local variables:" after the last "?\n?\f".

;; Local Variables:
;; indent-tabs-mode: nil
;; End:
;;; early-init.el ends here
#+end_src

In order to get help in understanding the code block above in a buffer showing
the original [[info:org#Top][Org]] source file, type {{{kbd(C-c C-c)}}} after moving
point (or cursor) to one of the items of the list:
1. src_emacs-lisp[:results none]{(describe-variable 'load-prefer-newer)}
2. src_emacs-lisp[:results none]{(apropos-library "no-littering")}
3. src_emacs-lisp{(find-function #'hack-local-variables)}
to execute the code between the curly braces for access to help.  This shows
that *Emacs is a self-documenting editor.*

* [[info:emacs#Init File][Init File (info)]] header
:PROPERTIES:
:CUSTOM_ID: sec:init-file-header
:END:

The =user-init-file= header requires =cl-lib= and sets Emacs options.  It
consists of three parts in listing [[lst:1st-setopt-call]], [[lst:2nd-setopt-call]], and
[[lst:2nd-setopt-call]] in order to limit the length of the listings for exporting
to LaTeX.

The [[info:emacs#Init File][init file (info)]] does load the ~custom-file~ according to the recommendation
of [[info:emacs#Saving Customizations][saving customizations (info)]].

#+caption[Set the first set of Emacs options]:
#+caption: Set the first set of Emacs options.
#+name: lst:1st-setopt-call
#+begin_src emacs-lisp -n :results silent
;;; init.el --- user init file                    -*- lexical-binding: t -*-
;;; Commentary:
;;; Code:

(require 'cl-lib)

(when (< emacs-major-version 30)
  (error "This `init.el' requires at least Emacs-30"))

(setopt
 after-save-hook #'executable-make-buffer-file-executable-if-script-p
 column-number-mode t
 cursor-type 'box
 custom-file (locate-user-emacs-file "custom.el")
 ;; Known problem: EasyPG fails to save files encrypted with GnuPG v2.4.1.
 ;; Darwin: brew install gnupg@2.2
 epg-pinentry-mode 'loopback
 global-hl-line-mode t
 global-hl-line-sticky-flag t
 history-delete-duplicates t
 history-length 500
 indent-tabs-mode nil
 inhibit-startup-buffer-menu t
 inhibit-startup-screen t
 initial-scratch-message ""
 isearch-lazy-count t
 kill-ring-max 300
 lazy-count-prefix-format nil
 lazy-count-suffix-format " (%s/%s)"
 lazy-highlight-initial-delay 1.0
 mode-line-compact t
 next-error-message-highlight t
 recentf-max-saved-items 100
 recentf-mode t
 save-place-mode t
 savehist-additional-variables '(kill-ring) ; BUG!
 savehist-mode t
 scroll-bar-mode nil
 tab-always-indent 'complete
 tool-bar-mode nil
 tooltip-mode nil
 url-cookie-trusted-urls nil
 url-cookie-untrusted-urls '(".*")
 use-dialog-box nil
 use-short-answers t
 view-read-only t
 winner-mode t)
#+end_src

#+caption[Set the second set of Emacs options: pin packages to archives]:
#+caption: Set the second set of Emacs options: pin packages to archives.
#+name: lst:2nd-setopt-call
#+begin_src emacs-lisp -n :results silent
(setopt
 ;; See https://github.com/melpa/melpa#mirrors for official Melpa mirrors.
 ;; ("melpa" . "https://www.mirrorservice.org/sites/melpa.org/packages/")
 package-archives '(("gnu" . "https://elpa.gnu.org/packages/")
                    ("gnu-devel" . "https://elpa.gnu.org/devel/")
                    ("melpa" . "https://melpa.org/packages/")
                    ("melpa-stable" . "https://stable.melpa.org/packages/")
                    ("nongnu" . "https://elpa.nongnu.org/nongnu/"))
 package-install-upgrade-built-in nil
 ;; Pin packages to GNU ELPA or to MELPA STABLE for info and/or stability.
 package-pinned-packages  '((auctex . "gnu")
                            (citar . "melpa-stable")
                            (citar-embark . "melpa-stable")
                            (compat . "gnu")
                            (consult . "gnu")
                            (dash . "melpa-stable")
                            (debbugs . "gnu")
                            (denote . "gnu")
                            (embark . "gnu")
                            (embark-consult . "gnu")
                            (emms . "gnu")
                            (engrave-faces . "gnu-devel")
                            (f . "melpa-stable")
                            (forge . "melpa-stable")
                            (git-commit . "nongnu")
                            (keycast . "nongnu")
                            (magit . "nongnu")
                            (magit-section . "nongnu")
                            (marginalia . "gnu")
                            (osm . "gnu")
                            (parsebib . "melpa-stable")
                            (queue . "gnu")
                            (rainbow-mode . "gnu")
                            (realgud . "melpa")
                            (s . "melpa-stable")
                            (xr . "gnu")
                            (vertico . "gnu")
                            (with-editor . "nongnu")
                            (yasnippet . "gnu"))
 package-selected-packages '(no-littering))
#+end_src

#+caption[Set the third set of Emacs options: final tweaks]:
#+caption: Set the third set of Emacs options: final tweaks.
#+name: lst:3rd-setopt-call
#+begin_src emacs-lisp -n :results silent
;; To use different Org git repositories (org or gro):
;; (push (expand-file-name "~/VCS/org-mode/lisp") load-path)
;; Postpone loading Org after shadowing Org and sh-script faces below.

(when (eq system-type 'darwin)
  ;; Failed to initialize color list unarchiver: ...
  ;; BUG#32854 and BUG#70836: rm ~/Library/Colors/Emacs.clr
  ;; INSTALL file: '--without-dbus --without-gconf --without-gsettings'.
  (setopt ns-alternate-modifier nil
          ns-command-modifier 'meta
          ns-right-command-modifier 'super))
(when (eq window-system 'ns)
  (add-to-list 'initial-frame-alist '(height . 51))
  (add-to-list 'initial-frame-alist '(width . 180)))

(when (file-exists-p custom-file)
  (load custom-file))
#+end_src

* [[info:emacs#Package Installation][Install the selected packages (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:install-selected-packages
:END:

[[info:emacs#Package Installation][Emacs installs packages]] from archives on the internet.  This setup uses five
archives:
1. The [[https://elpa.gnu.org/][GNU Emacs Lisp Package Archive]].
2. The [[https://elpa.gnu.org/devel/index.html][Development Emacs Lisp Package Archive]].
3. The [[https://elpa.nongnu.org/][NonGNU Emacs Lisp Package Archive]].
4. The [[https://melpa.org/#/][Milkypostman's Emacs Lisp Package Archive (MELPA)]] with its official
   [[https://www.mirrorservice.org/sites/melpa.org/packages/][mirror]] in case [[https://downforeveryoneorjustme.com/melpa.org][is Melpa.org down?]] tells [[https://melpa.org/#/][MELPA]] is down for everyone.
5. The [[https://stable.melpa.org/#/getting-started][Stable Milkypostman's Emacs Lisp Package Archive]].

The code in listing [[lst:install-selected-packages]] assumes that the package
system is in a *virgin* state if the package [[https://github.com/emacscollective/no-littering][no-littering]] is not present:
1. It installs and loads [[https://github.com/emacscollective/no-littering][no-littering]] after ensuring refreshing of the
   contents of available packages.
2. It calls src_emacs-lisp[:results silent]{(package-install-selected-packages)}
   to check the installation status of all packages in src_emacs-lisp[:results
   silent]{package-selected-packages} and to install the missing packages after
   the user has agreed to its prompt.
3. It defines a function to ensure the installation of packages in other source
   blocks.
In case of normal Emacs usage, src_emacs-lisp[:results silent]{(list-packages)}
refreshes the contents of packages and allows to update packages to the latest
version.

#+caption[Install the selected packages]:
#+caption: Install the selected packages.
#+name: lst:install-selected-packages
#+begin_src emacs-lisp -n :results silent
(defvar package-selected-packages)

(unless noninteractive
  (unless (require 'no-littering nil 'noerror)
    (unless (bound-and-true-p package-archive-contents)
      (package-refresh-contents))
    ;; Install and require `no-littering'.
    (package-install 'no-littering)
    (require 'no-littering)
    ;; Install the selected packages.
    (package-install-selected-packages)))

(defun ensure-package-selection (package)
  "Ensure selection of PACKAGE."
  (when (and (package-installed-p package)
             (bound-and-true-p package-selected-packages))
    (cl-pushnew package package-selected-packages)))

(defun ensure-package-installation (&rest packages)
  "Ensure installation of all packages in PACKAGES."
  (let ((ok t))
    (dolist (package packages)
      (unless (package-installed-p package)
        (package-install package))
      (unless (ensure-package-selection package)
        (setq ok nil)))
    ok))
#+end_src

* [[https://git.savannah.gnu.org/cgit/emacs.git/tree/admin/notes/tree-sitter/starter-guide?h=feature/tree-sitter][Emacs Tree-sitter]]
:PROPERTIES:
:CUSTOM_ID: sec:emacs-tree-sitter
:END:

Mickey Peterson's post [[https://www.masteringemacs.org/article/how-to-get-started-tree-sitter?utm_source=newsletter&utm_medium=rss][How To Get Started with Tree-Sitter]] explains how to use
=tree-sitter= in Emacs-29.1.  Listing [[lst:setup-treesit-sources][Setup =treesit= grammar sources]] configures
where to find the different =tree-sitter= grammar sources for different
languages.  Listing [[lst:setup-go][Setup Go programming]] shows how to configure ~tab-width~ for
~go-ts-mod~ and ~go-mode-ts-mode~.

#+caption[Setup =treesit= grammar sources]:
#+caption: Setup =treesit= grammar sources.
#+name: lst:setup-treesit-sources
#+begin_src emacs-lisp -n :results silent
(when (require 'treesit nil 'noerror)
  (setopt
   treesit-language-source-alist
   '((bash "https://github.com/tree-sitter/tree-sitter-bash" "master" "src")
     (c "https://github.com/tree-sitter/tree-sitter-c" "master" "src")
     (cmake "https://github.com/uyha/tree-sitter-cmake" "master" "src")
     (cpp "https://github.com/tree-sitter/tree-sitter-cpp" "master" "src")
     (css "https://github.com/tree-sitter/tree-sitter-css" "master" "src")
     (glsl "https://github.com/theHamsta/tree-sitter-glsl" "master" "src")
     ;; go-ts-mode requires libtree-sitter-go and libtree-sitter-gomode.
     (go "https://github.com/tree-sitter/tree-sitter-go" "master" "src")
     (gomod "https://github.com/camdencheek/tree-sitter-go-mod" "main" "src")
     (html "https://github.com/tree-sitter/tree-sitter-html" "master" "src")
     (java "https://github.com/tree-sitter/tree-sitter-java" "master" "src")
     (javascript "https://github.com/tree-sitter/tree-sitter-javascript"
                 "master" "src")
     (json "https://github.com/tree-sitter/tree-sitter-json" "master" "src")
     (julia "https://github.com/tree-sitter/tree-sitter-julia" "master" "src")
     (lua "https://github.com/MunifTanjim/tree-sitter-lua" "main" "src")
     (make "https://github.com/alemuller/tree-sitter-make" "main" "src")
     (perl "https://github.com/ganezdragon/tree-sitter-perl" "master" "src")
     (python "https://github.com/tree-sitter/tree-sitter-python" "master" "src")
     (ruby "https://github.com/tree-sitter/tree-sitter-ruby" "master" "src")
     (rust "https://github.com/tree-sitter/tree-sitter-rust" "master" "src")
     (scala "https://github.com/tree-sitter/tree-sitter-scala" "master" "src")
     (sql "https://github.com/m-novikov/tree-sitter-sql" "main" "src")
     (swift "https://github.com/tree-sitter/tree-sitter-swift" "master" "src")
     (toml "https://github.com/tree-sitter/tree-sitter-toml" "master" "src")
     (tsx "https://github.com/tree-sitter/tree-sitter-typescript"
          "master" "tsx/src")
     (typescript "https://github.com/tree-sitter/tree-sitter-typescript"
                 "master" "typescript/src")
     (yaml "https://github.com/ikatyang/tree-sitter-yaml" "master" "src"))))
#+end_src

* [[info:emacs#Faces][Text faces or styles (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:text-faces-or-styles
:END:

This setup does not use [[info:emacs#Custom Themes][custom themes (info)]], but it does a minimal setup of
fonts and faces.  The [[https://protesilaos.com/codelog/2020-09-05-emacs-note-mixed-font-heights/][note on mixed font heights in Emacs]] for how to setup fonts
properly.  It boils down to two rules:
1. The height of the default face must be an integer number to make the height a
   physical quantity.
2. The heights of all other faces must be real numbers to scale those heights
   with respect to the height of the face (those heights default to 1.0 for no
   scaling).
The code in listing [[lst:configure-face-attributes]] implements those rules.
Listing [[lst:face-setting-functions]] shows that font scaling is easy in case of
proper initialization of all face heights in a frame.  To adjust the font size
in windows, invoke src_emacs-lisp{(set-default-face-height)}.  To adjust the
font size in the current buffer, type {{{kbd(s-=)}}} or {{{kbd(s-+)}}} to invoke
src_emacs-lisp[:results silent]{(text-scale-adjust +1)} before making further
adjustments as displayed.  Listing [[lst:face-setting-functions]],
[[lst:shadow-org-font-lock-faces]], and [[lst:shadow-emacs-font-lock-faces]] show tweaks
to improve visibility without theming:
1. Toggling between a dark and light background by means of
   src_emacs-lisp{(invert-default-face)}.
2. Shadowing the definition of faces before loading.  The last item in the page
   on [[https://orgmode.org/worg/org-contrib/babel/examples/fontify-src-code-blocks.html#org5c4406f][fontifying Org mode source code blocks]] describes this method.
Listing [[lst:use-buffer-face-mode-for-fixed-or-variable-pitch-face]] contains
functions to set a fixed or variable pitch face in the current buffer and
selects a fixed pitch face for =magit-mode= and =progmode= buffers.  Type
{{{kbd(M-x describe-text-properties)}}} to inspect faces at point.  Listing
[[lst:disable-mac-mouse-change-font-size]] tries to disable accidental changing of
the font size with the mouse on Darwin.  Listing [[lst:setup-visual-line-mode]]
configures =visual-line-mode=.

#+caption[Configure =face-attributes=]:
#+caption: Configure =face-attributes=.
#+name: lst:configure-face-attributes
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  ;; Set face attributes.
  (cond
   ((eq system-type 'darwin)
    (set-face-attribute 'default nil :family "Hack" :height 120)
    (set-face-attribute 'fixed-pitch nil :family "Hack")
    (set-face-attribute 'variable-pitch nil :family "FiraGo"))
   ((eq system-type 'gnu/linux)
    (set-face-attribute 'default nil :family "Hack" :height 110)
    (set-face-attribute 'fixed-pitch nil :family "Hack")
    (set-face-attribute 'variable-pitch nil :family "FiraGo"))
   (t
    (set-face-attribute 'default nil :family "Hack" :height 110)
    (set-face-attribute 'fixed-pitch nil :family "Hack")
    (set-face-attribute 'variable-pitch nil :family "DejaVu Sans"))))
#+end_src

#+caption[Implement =face= setting functions]:
#+caption: Implement =face= setting functions.
#+name: lst:face-setting-functions
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  ;; Neither `set-default-face-height' nor `text-scale-adjust' work well.
  (defun set-default-face-height ()
    "Set the default face height in all current and future frames.

Scale all other faces with a height that is a real number."
    (interactive)
    (let* ((prompt (format "face height (%s): "
                           (face-attribute 'default :height)))
           (choices (mapcar #'number-to-string
                            (number-sequence 50 200 10)))
           (height (string-to-number
                    (completing-read prompt choices nil 'require-match))))
      (message "Setting the height of the default face to %s" height)
      (set-face-attribute 'default nil :height height)))

  (defun invert-default-face ()
    "Invert the default face."
    (interactive)
    (invert-face 'default)))
#+end_src

#+caption[Shadow Org font-lock faces to improve the readability]:
#+caption: Shadow Org font-lock faces to improve the readability.
#+name: lst:shadow-org-font-lock-faces
#+begin_src emacs-lisp -n
;; Shadow two definitions in org-faces.el:
(defface org-block
  ;; https://emacs.stackexchange.com/a/9604 answers:
  ;; How to override a defined face for light and dark backgrounds?
  `((((background dark))
     :inherit (fixed-pitch)
     ,@(and (>= emacs-major-version 27) '(:extend t))
     :background "#444444")
    (t
     :inherit (fixed-pitch)
     ,@(and (>= emacs-major-version 27) '(:extend t))
     :background "#FFFFD0"))
  "My face used for text inside blocks.

It is always used for source blocks.  You can refine what face
should be used depending on the source block language by setting,
`org-src-block-faces', which takes precedence.

When `org-fontify-quote-and-verse-blocks' is not nil, text inside
verse and quote blocks are fontified using the `org-verse' and
`org-quote' faces, which inherit from `org-block'."
  :group 'org-faces)

(defface org-table
  ;; https://emacs.stackexchange.com/a/9604 answers:
  ;; How to override a defined face for light and dark backgrounds?
  `((((background dark))
     :inherit (fixed-pitch)
     ,@(and (>= emacs-major-version 27) '(:extend t))
     :background "#444444")
    (t
     :inherit (fixed-pitch)
     ,@(and (>= emacs-major-version 27) '(:extend t))
     :background "#FFFFD0"))
  "My face for tables."
  :group 'org-faces)
#+end_src

#+caption[Shadow Emacs font-lock faces to improve the readability]:
#+caption: Shadow Emacs font-lock faces to improve the readability.
#+name: lst:shadow-emacs-font-lock-faces
#+begin_src emacs-lisp -n
;; Shadow one definition in sh-script.el:
(defface sh-heredoc
  '((((class color) (background dark))
     (:foreground "yellow"))
    (((class color) (background light))
     (:foreground "magenta"))
    (t
     (:weight bold)))
  "My face to show a here-document."
  :group 'sh-indentation)
#+end_src

#+caption[Use =buffer-face-mode= to set fixed or variable pitch face]:
#+caption: Use =buffer-face-mode= to set fixed or variable pitch face.
#+name: lst:use-buffer-face-mode-for-fixed-or-variable-pitch-face
#+begin_src emacs-lisp -n
;; Use proportional font faces in current buffer
(defun set-buffer-variable-pitch-face ()
  "Set a variable width (proportional) font in current buffer."
  (interactive)
  (setq-local buffer-face-mode-face 'variable-pitch)
  (buffer-face-mode))

;; Use monospaced font faces in current buffer
(defun set-buffer-fixed-pitch-face ()
  "Set a fixed width (monospace) font in current buffer."
  (interactive)
  (setq-local buffer-face-mode-face 'fixed-pitch)
  (buffer-face-mode))

(add-hook 'magit-mode-hook #'set-buffer-fixed-pitch-face)
(add-hook 'prog-mode-hook #'set-buffer-fixed-pitch-face)
#+end_src

#+caption[Disable changing font size with mouse on Darwin]:
#+caption: Disable changing font size with mouse on Darwin.
#+name: lst:disable-mac-mouse-change-font-size
#+begin_src emacs-lisp -n :results silent
(when (eq system-type 'darwin)
  ;; https://lmno.lol/alvaro/hey-mouse-dont-mess-with-my-emacs-font-size
  ;; Hint: reset font size with "C-u 0 M-x text-scale-adjust".
  ;; GAV: how to explain undefined "C-<wheel-left>" and "C-<wheel-right>"?
  (global-set-key (kbd "<pinch>") 'ignore)
  (global-set-key (kbd "<C-wheel-up>") 'ignore)
  (global-set-key (kbd "<C-wheel-down>") 'ignore))
#+end_src

#+caption[Setup ~visual-line-mode~]:
#+caption: Setup ~visual-line-mode~.
#+name: lst:setup-visual-line-mode
#+begin_src emacs-lisp -n :results silent
(when (fboundp 'visual-wrap-prefix-mode)
  (add-hook 'visual-line-mode-hook 'visual-wrap-prefix-mode))
#+end_src

* [[info:emacs#Windows][Window management (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:window-management
:END:

Mickey Peterson's post [[https://www.masteringemacs.org/article/demystifying-emacs-window-manager][Demystifying Emacs's Window Manager]] invites to improve
window placement.  Listing [[lst:1st-window-management]] and
[[lst:2nd-window-management]] implement a selection of his recommendations.  See:
1. [[info:elisp#The Zen of Buffer Display][The Zen of Buffer Display (info)]]
2. [[https://e17i.github.io/articles-emacs-display-1/][Configuring the Emacs display system]]
for technical information.

#+caption[Window management functions and key bindings]:
#+caption: Window management functions and key bindings.
#+name: lst:1st-window-management
#+begin_src emacs-lisp -n
(with-eval-after-load 'emacs
  ;; https://www.masteringemacs.org/article/demystifying-emacs-window-manager
  (defun split-root-below (arg)
    "Split window below from the root or from the parent with ARG."
    (interactive "P")
    (split-window (if arg
                      (window-parent (selected-window))
                    (frame-root-window))
                  nil 'below nil))

  (defun split-root-right (arg)
    "Split window right from the root or from the parent with ARG."
    (interactive "P")
    (split-window (if arg
                      (window-parent (selected-window))
                    (frame-root-window))
                  nil 'right nil))

   (defun toggle-window-dedication ()
    "Toggles window dedication in the selected window."
    (interactive)
    (set-window-dedicated-p
     (selected-window) (not (window-dedicated-p (selected-window)))))

   (defun make-display-buffer-matcher-function (major-modes)
    "Return a lambda function to match a list of MAJOR-MODES."
    (lambda (buf-name _action)
      (with-current-buffer buf-name (apply #'derived-mode-p major-modes))))

   (keymap-global-set "M-o" #'other-window))
#+end_src

#+caption[Window management variables]:
#+caption: Window management variables.
#+name: lst:2nd-window-management
#+begin_src emacs-lisp -n :results none
;; (info "(elisp) Displaying Buffers")
;; (info "(emacs) Window Choice")
;; (describe-function 'display-buffer)
(with-eval-after-load 'emacs
  ;; https://www.masteringemacs.org/article/demystifying-emacs-window-manager
  (setopt switch-to-buffer-obey-display-actions t)
  (add-to-list 'display-buffer-alist
               `(,(rx (or "*Apropos*" "*Dictionary*"))
                 (display-buffer-reuse-window display-buffer-pop-up-window)
                 (inhibit-same-window . nil)))
  (add-to-list 'display-buffer-alist
               `(,(rx (or "*Help*" "*info*"))
                 display-buffer-pop-up-window
                 (inhibit-same-window . t)))
  (add-to-list 'display-buffer-alist
               `(,(rx (or "*Occur*" "*grep*" "*xref*"))
                 display-buffer-reuse-window
                 (inhibit-same-window . nil)))
  ;; BUG#70773: Eli tells `(setq delayed-warnings-hook nil)' is better.
  ;; BUG#70795: Inconsistent `warning-display-at-bottom' behavior.
  ;; https://lists.gnu.org/archive/html/bug-gnu-emacs/2024-05/msg00359.html
  ;; Works now always as after setting `warnings-display-at-bottom' to `nil'.
  (add-to-list 'display-buffer-alist
               `(,(rx (or "*Warnings*" "*compilation*"))
                 display-buffer-no-window
                 (allow-no-window . t))))
#+end_src

* [[info:emacs#Bookmarks][Bookmarks (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:bookmarks
:END:

Listing [[lst:setup-bookmark][bookmark setup]] preserves bookmark history in [[./var/bookmark-default.el][bookmark-default.el]].  Table
[[tab:bookmark-commands-and-bindings]] lists all =bookmark= commands with working
key bindings.  Not all key bindings in src_emacs-lisp[:results
silent]{(describe-variable 'bookmark-map)} are operational for different
reasons.

BUG: The virtual buffers of the ~consult-buffer~ command do not seem to work.
Therefore, ~consult-buffer~ is no means to access the bookmark history (contrary
to claims in [[info:consult#Top][consult (info)]]).

#+caption[Let Emacs save bookmarks when killed]:
#+caption: Let Emacs save bookmarks when killed.
#+name: lst:setup-bookmark
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'bookmark
  (setopt bookmark-save-flag 1)
  (setf bookmark-exit-hook 'bookmark-unload-function))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Bookmark commands with key bindings]:
#+caption: Bookmark commands with key bindings.
#+name: tab:bookmark-commands-and-bindings
|------------------------------+--------------------|
| command                      | key binding        |
|------------------------------+--------------------|
| *bookmark-delete*            |                    |
| *bookmark-delete-all*        |                    |
| *bookmark-insert*            | {{{kbd(C-x r i)}}} |
| *bookmark-insert-location*   |                    |
| *bookmark-jump*              | {{{kbd(C-x r j)}}} |
| *bookmark-jump-other-frame*  |                    |
| *bookmark-jump-other-window* |                    |
| *bookmark-load*              |                    |
| *bookmark-rename*            |                    |
| *bookmark-save*              |                    |
| *bookmark-set*               | {{{kbd(C-x r m)}}} |
| *bookmark-set-no-overwrite*  | {{{kbd(C-x r M)}}} |
| *bookmark-write*             |                    |
| *consult-bookmark*           | {{{kbd(C-x r b)}}} |
| *list-bookmarks*             |                    |
|------------------------------+--------------------|

* [[info:emacs#Registers][Registers (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:registers
:END:

Listing [[lst:register-separator-usage-example][register separator usage example]] shows how to use a register
{{{kbd(+)}}} as register separator when appending regions to text registers.
Listing [[lst:setup-register][setup register usage]] prepares my preferred register usage.  Table
[[tab:register-commands-and-bindings]] lists all =register= commands with working
key bindings.  The =desktop= library allows to preserve the =register= history
between Emacs sessions.

#+caption[Register separator usage example]:
#+caption: Register separator usage example.
#+name: lst:register-separator-usage-example
#+begin_src text -n :exports code
When I set register ?+ to
(set-register ?+ "\n*REGISTER SEPARATOR*\n")
to test append-to-register on two regions like
Mark this line without new-line as region 1
Mark this line without new-line as region 2
The correct result of
"C-x r s T" with region 1 marked
"C-x r + T" with region 2 marked
"C-x r i T"
is:
Mark this line without new-line as region 1
*REGISTER SEPARATOR*
Mark this line without new-line as region 2
#+end_src

#+caption[Setup register usage]:
#+caption: Setup register usage.
#+name: lst:setup-register
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'register
  ;; Register `?+' serves as register separator when using `append-to-register':
  (set-register ?+ "\n")

  ;; https://emacs.stackexchange.com/a/52290
  (defun delete-all-registers ()
    "Delete all registers."
    (interactive)
    (setq register-alist nil)))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Register commands with key bindings]:
#+caption: Register commands with key bindings.
#+name: tab:register-commands-and-bindings
|------------------------------------+------------------------|
| command                            | key binding            |
|------------------------------------+------------------------|
| *append-to-register*               |                        |
| *copy-rectangle-to-register*       | {{{kbd(C-x r r)}}}     |
| *copy-to-register*                 | {{{kbd(C-x r s)}}}     |
| *frameset-to-register*             | {{{kbd(C-x r f)}}}     |
| *increment-register*               | {{{kbd(C-x r +)}}}     |
| *insert-register*                  | {{{kbd(C-x r i)}}}     |
| *jump-to-register*                 | {{{kbd(C-x r j)}}}     |
| *kmacro-to-register*               | {{{kbd(C-x C-k x)}}}   |
| *number-to-register*               | {{{kbd(C-x r n)}}}     |
| *point-to-register*                | {{{kbd(C-x r <SPC>)}}} |
| *prepend-to-register*              |                        |
| *set-register*                     |                        |
| *window-configuration-to-register* | {{{kbd(C-x r w)}}}     |
|------------------------------------+------------------------|

* [[info:emacs#Dired][Dired: directory editor as file manager (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:file-manager
:END:

[[info:emacs#Dired][Dired (info)]] and the [[https://github.com/ranger/ranger#readme][ranger]] file manager offer similar capabilities for copying,
deleting, opening, renaming, and viewing files and directories, but the
integration of [[info:emacs#Dired][dired (info)]] in Emacs is obviously much better than the
integration of [[https://github.com/ranger/ranger#readme][ranger]] in Emacs.

For instance, this setup allows to insert an =org-mode= link to a file
containing a specific image into an =org-mode= buffer by means of the facilities
of [[info:emacs#Dired][dired (info)]] as follows:
1. Type {{{kbd(C-x d)}}} to open the directory containing the file with the
   specific image in a =dired-mode= buffer.
2. Start searching for the specific image by navigating to the name of any image
   file.
3. Type {{{kbd(v)}}} to switch to view the file in an =image-mode= buffer.
4. In the =image-mode= buffer, continue searching for the specific image by
   typing:
   - {{{kbd(n)}}} to view the next image in the =dired-mode= buffer,
   - {{{kbd(p)}}} to view the previous image in the =dired-mode= buffer, and
   - {{{kbd(q)}}} to quit the =image-mode= buffer and to go back to the
     =dired-mode= buffer.
5. After finding the specific image, use {{{kbd(C-c l)}}} in the =image-mode=
   buffer or the =dired-mode= buffer to store the =org-link=.
6. Switch to the =org-mode= buffer and use {{{kbd(C-c C-l)}}} to insert the
   =org-link= into the buffer.

Listing [[lst:set-dired-options]] makes the directory editor sort entries
alphabetically after grouping the directories before grouping the files by
extension.

#+caption[Set =dired= options]:
#+caption: Set =dired= options.
#+name: lst:set-dired-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'dired
  (setopt dired-dwim-target t
          ;; | switch | action                                 |
          ;; |--------+----------------------------------------|
          ;; | -a     | also list hidden entries               |
          ;; | -l     | use a long listing format              |
          ;; | -X     | sort alphabetically by entry extension |
          ;; | -G     | skip long listing format group names   |
          ;; | -1     | list one entry per line                |
          dired-listing-switches "-alGX1 --group-directories-first"
          dired-recursive-copies 'always
          dired-recursive-deletes 'always))

(with-eval-after-load 'wdired
  (setopt wdired-allow-to-change-permissions t))
#+end_src

Listing [[lst:extra-dired-key-bindings]] adds a new key binding to =dired-mode-map=
to open files with the [[https://en.wikipedia.org/wiki/Eww_(web_browser)][Emacs Web Wowser]] inside Emacs.

#+caption[Extra =dired= key bindings]:
#+caption: Extra =dired= key bindings.
#+name: lst:extra-dired-key-bindings
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'dired
  (defun dired-eww-open-file ()
    "In Dired, open the regular file named on this line with eww"
    (interactive)
    (let ((file (dired-get-file-for-visit)))
      (if (file-regular-p file)
          (eww-open-file file)
        (error "Eww rejects `%s', since it is not a regular file" file))))

  (keymap-set dired-mode-map "E" #'dired-eww-open-file))
#+end_src

* [[info:emacs#Completion Styles][Minibuffer completion styles (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:minibuffer-completion-styles
:END:

Listing [[lst:set-minibuffer-options][set minibuffer options]] implements ideas of the post [[https://www.masteringemacs.org/article/understanding-minibuffer-completion][Understanding
minibuffer completion]].

#+caption[Set =minibuffer= options]:
#+caption: Set =minibuffer= options.
#+name: lst:set-minibuffer-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'minibuffer
  ;; https://www.masteringemacs.org/article/understanding-minibuffer-completion
  (setopt
   completion-category-overrides '((file (styles basic substring)))
   completion-styles '(basic flex partial-completion substring)))
#+end_src

* [[info:elisp#Processes][Processes (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:processes
:END:

Listing [[lst:process-utilities]] defines a function to run a (command-line) program
with arguments and to obtain a list with its numeric exit status as well as its
output to =stdout=.

#+caption[Process utilities]:
#+caption: Process utilities.
#+name: lst:process-utilities
#+begin_src emacs-lisp -n :results silent
;; https://gitlab.com/howardabrams/spacemacs.d/blob/master/layers/ha-org/funcs.el#L418
(defun shell-command-with-exit-code (program &rest args)
  "Run PROGRAM with ARGS and return exit-code and output in a list."
  (with-temp-buffer
    (list (apply 'call-process program nil (current-buffer) nil args)
          (buffer-substring-no-properties (point-min) (point-max)))))
#+end_src

* [[info:emacs#Help][Help (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:help
:END:

Listing [[lst:setup-help]] enriches the help buffer.  Table [[tab:help-key-bindings]]
lists a number of key bindings to start playing with the help facilities of
Emacs.  Try {{{kbd(C-h o)}}} instead of {{{kbd(C-h f)}}} or {{{kbd(C-h v)}}}.

#+caption[Setup =help=]:
#+caption: Setup =help=.
#+name: lst:setup-help
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'help-fns
  ;; ChatGPT recommends to require `shortdoc' contrary to the
  ;; `shortdoc-help-fns-examples-function' documentation string.
  ;; BUG#71537: "emacs -Q" works with a simpler `add-hook' form. Note:
  ;; `add-hook' should append `shortdoc-help-fns-examples-function' to
  ;; `help-fns-describe-function-functions'.
  (add-hook 'help-fns-describe-function-functions
            #'shortdoc-help-fns-examples-function 'append)
  (setopt help-enable-symbol-autoload t))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Help key bindings]:
#+caption: Help key bindings.
#+name: tab:help-key-bindings
|------------------------------+----------+------------------|
| command                      | key map  | keys             |
|------------------------------+----------+------------------|
| Info-goto-emacs-command-node | help-map | {{{kbd(C-h F)}}} |
| describe-function            | help-map | {{{kbd(C-h f)}}} |
| describe-key                 | help-map | {{{kbd(C-h k)}}} |
| describe-symbol              | help-map | {{{kbd(C-h o)}}} |
| describe-variable            | help-map | {{{kbd(C-h v)}}} |
| info                         | help-map | {{{kbd(C-h i)}}} |
|------------------------------+----------+------------------|

** [[info:emacs#Name Help][Shortdoc-display-group (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:shortdoc-display-group
:END:

Listing [[lst:setup-shortdoc]] binds {{{kbd(C-h y)}}} to =shortdoc-display-group=.

#+caption[Setup =shortdoc=]:
#+caption: Setup =shortdoc=.
#+name: lst:setup-shortdoc
#+begin_src emacs-lisp -n :results silent
(when (fboundp 'shortdoc-display-group)
  (keymap-set help-map "y" #'shortdoc-display-group))
#+end_src

** [[info:info#Top][Info (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:info
:END:

Listing [[lst:configure-info]] adds the required paths to the places where =info=
looks for files.

#+caption[Configure =info=]:
#+caption: Configure =info=.
#+name: lst:configure-info
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'info
  ;; Make Emacs find ALL "*.info" files in `package-user-dir' on Gentoo Linux.
  (when (eq system-type 'gnu/linux)
    (dolist (path
             (nreverse
              (mapcar
               (lambda (name)
                 (expand-file-name (file-name-directory name)))
               (directory-files-recursively package-user-dir "\\.info\\'"))))
      (add-to-list 'Info-directory-list path nil #'file-equal-p)))
  ;; Make Emacs find the git Org info files.
  ;; (push (expand-file-name "~/VCS/org-mode/doc") Info-directory-list)
  ;; Make Emacs find Python info files.
  (push (expand-file-name "~/.local/share/info") Info-directory-list))
#+end_src

* [[info:emacs#Key Bindings][Key bindings (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:key-bindings
:END:

#+attr_latex: :booktabs yes :float table
#+caption[Basic key bindings]:
#+caption: Basic key bindings.
#+name: tab:basic-key-bindings
|--------------------+------------+------------------------|
| command            | key map    | keys                   |
|--------------------+------------+------------------------|
| undo               | global-map | {{{kbd(s-z)}}}         |
| backward-kill-word | global-map | {{{kbd(C-backspace)}}} |
| backward-char      | global-map | {{{kbd(C-b)}}}         |
| forward-char       | global-map | {{{kbd(C-f)}}}         |
| backward-word      | global-map | {{{kbd(M-b)}}}         |
| forward-word       | global-map | {{{kbd(M-f)}}}         |
| backward-sentence  | global-map | {{{kbd(M-a)}}}         |
| forward-sentence   | global-map | {{{kbd(M-e)}}}         |
|--------------------+------------+------------------------|

** [[info:emacs#Disabling][Disabling Commands (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:enable-disabled-commands
:END:

Execute src_emacs-lisp[:results none]{(find-library "novice")} to see how Emacs
prevents new users from shooting themselves in the feet.  Listing
[[lst:configure-disabled-command-function]] enables [[https://www.emacswiki.org/emacs/DisabledCommands][disabled commands on the fly]].

#+caption[Configure the =disabled-command-function=]:
#+caption: Configure the =disabled-command-function=.
#+name: lst:configure-disabled-command-function
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (setq disabled-command-function
        (defun enable-this-command (&rest _args)
          "Called when executing a disabled command.
Enable it and re-execute it."
          (put this-command 'disabled nil)
          (message "You typed %s.  Emacs enabled %s."
                   (key-description (this-command-keys)) this-command)
          (sit-for 0)
          (call-interactively this-command))))
#+end_src

** [[https://github.com/michael-heerdegen/interaction-log.el#readme][Interaction-log]]
:PROPERTIES:
:CUSTOM_ID: sec:interaction-log
:END:

#+caption[Configure =interaction-log=]:
#+caption: Configure =interaction-log=.
#+name: lst:configure-interaction-log
#+begin_src emacs-lisp -n :results silent
(when (and (ensure-package-installation 'interaction-log)
           (require 'interaction-log nil 'noerror))

  ;; https://www.skybert.net/emacs/show-shortcuts-when-giving-presentations/
  (defun ilog-ensure-ilog-buffer-window ()
    "Ensure the visibility of the `ilog' buffer, when it exists."
    (when (and (get-buffer ilog-buffer-name)
               (not (get-buffer-window ilog-buffer-name)))
      (display-buffer (get-buffer ilog-buffer-name))))

  (keymap-set help-map "C-l" #'interaction-log-mode)
  (advice-add 'ilog-timer-function :after #'ilog-ensure-ilog-buffer-window))
#+end_src


** [[https://github.com/tarsius/keycast#readme][Keycast]]
:PROPERTIES:
:CUSTOM_ID: sec:keycast
:END:

Listing [[lst:configure-keycast]] configures =keycast=.

#+caption[Configure =keycast=]:
#+caption: Configure =keycast=.
#+name: lst:configure-keycast
#+begin_src emacs-lisp -n :results silent
;; Make `keycast-log-update-buffer' use a buffer similar to the
;; control buffer `ediff-setup-windows-plain' returns.
(when (ensure-package-installation 'keycast)
  (setopt keycast-log-newest-first t
          keycast-mode-line-window-predicate #'keycast-bottom-right-window-p)

  (defun keycast-log-update-buffer-plain ()
    (let ((buffer (get-buffer keycast-log-buffer-name)))
      (unless (buffer-live-p buffer)
        (setq buffer (get-buffer-create keycast-log-buffer-name))
        (with-current-buffer buffer
          (setq buffer-read-only t)))
      (unless (get-buffer-window buffer)
        (display-buffer buffer '(display-buffer-at-bottom
                                 (dedicated . t)
                                 (window-height . 10))))
      (when-let ((output (keycast--format keycast-log-format)))
        (with-current-buffer buffer
          (goto-char (if keycast-log-newest-first (point-min) (point-max)))
          (let ((inhibit-read-only t))
            (when (and (> keycast--command-repetitions 0)
                       (string-match-p "%[rR]" keycast-log-format))
              (unless keycast-log-newest-first
                (backward-char))
              (ignore-errors
                (delete-region (line-beginning-position)
                               (1+ (line-end-position)))))
            (insert output))
          (goto-char (if keycast-log-newest-first (point-min) (point-max)))))))

  (advice-add 'keycast-log-update-buffer
              :override #'keycast-log-update-buffer-plain))
#+end_src

* [[info:emacs#Emacs Server][Using Emacs as a server (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:using-emacs-server
:END:

Emacs can act as a server that listens to a socket to share its state (for
instance buffers and command history) with other programs by means of a shell
command =emacsclient=.  Section [[#sec:latexmk-save-compile-display-loop]] how to
use ~emacsclient~ to install an asynchronous (or background) loop of saving a
LaTeX file, compiling it, and redisplaying the output in Emacs.

#+caption[Start the Emacs server]:
#+caption: Start the Emacs server.
#+name: lst:start-emacs-server
#+begin_src emacs-lisp -n :results silent
(when window-system
  (unless (or noninteractive (daemonp))
    (add-hook 'after-init-hook #'server-start)))
#+end_src

** Latexmk save-compile-display loop
:PROPERTIES:
:CUSTOM_ID: sec:latexmk-save-compile-display-loop
:END:

The =latexmk= resource file in the next source code block shows how to use
=emacsclient= to (re)display the PDF file in Emacs after each successful
(re)compilation on condition that the local ~compile-command~ variable is
correct.  The local ~compile-command~ variable in the [[#sec:local-variables][local variables]] section
(only visible in =org= files, but not in =html= and =pdf= files) shows how to
make use of the =latexmkrc= file.

#+attr_latex: :options breaklines
#+caption[Tangle the =Latexmk= resource file]:
#+caption: Tangle the =Latexmk= resource file.
#+name: lst:latexmkrc
#+begin_src perl -n :tangle latexmkrc :comments no
# pdf creator
$pdf_mode = 4;  # 4 means lualatex
# pdf previewer and update pdf previewer
$pdf_previewer = "emacsclient -e '(find-file-other-window %S)'";
$pdf_update_method = 4;  # 4 runs $pdf_update_command to force the update
$pdf_update_command = "emacsclient -e '(with-current-buffer (find-buffer-visiting %S) (pdf-view-revert-buffer nil t))'";
# see for instance glossary.latexmkrc
add_cus_dep( 'acn', 'acr', 0, 'makeglossaries' );
add_cus_dep( 'glo', 'gls', 0, 'makeglossaries' );
# use ".=" to append to $clean_ext
$clean_ext .= " acr acn alg bbl dvi glo gls glg ist lol lst";
$clean_ext .= " nav run.xml snm synctex.gz";
sub makeglossaries {
    my ($name, $path) = fileparse( $$Psource );
    return system "makeglossaries -d '$path' '$name'";
}
# Emacs looks for "Local variables:" after the last "newline-formfeed".

# Local Variables:
# mode: perl
# End:
#+end_src

** TODO Org-protocol handling with other browser on Darwin         :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:org-protocol-darwin
:END:

1. [[http://rwx.io/posts/osx-uri-protocol-handler/][Patrick Goddi: macOS URI protocol handler]] and his [[https://github.com/fooqri/uri-handler][URI-Handler]].
2. [[https://www.hammerspoon.org/][Hammerspoon]]
3. [[https://vritser.github.io/posts/capture-anywhere/][Emacs Capture Anywhere]]

* [[info:emacs#Calendar/Diary][Calendar, Diary, and Time (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:time
:END:

#+caption[Set =world-clock= options]:
#+caption: Set =world-clock= options.
#+name: lst:set-world-clock-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'time
  (setopt world-clock-list
          '(("America/Los_Angeles" "Seattle")
            ("America/New_York" "New York")
            ("Europe/London" "London")
            ("Europe/Moscow" "Moscow")
            ("Europe/Paris" "Paris")
            ("Europe/Istanbul" "Istanbul")
            ("Africa/Cairo" "Cairo")
            ("Asia/Jerusalem" "Jerusalem")
            ("Asia/Singapore" "Singapore")
            ("Asia/Tokyo" "Tokyo"))
          world-clock-time-format "%a %d %b %R %z"))
#+end_src

* Tools to handle buffers and modes
:PROPERTIES:
:CUSTOM_ID: sec:buffer-mode-tools
:END:

#+caption[Tools to handle buffers and modes]:
#+caption: Tools to handl buffers and modes.
#+name: lst:buffer-mode-tools
#+begin_src emacs-lisp -n :results silent
(defun set-all-buffers-with-modes (minor-mode value modes)
  "Set MINOR-MODE to VALUE for all buffers with a mode derived from MODES."
  (dolist (buffer (buffer-list))
    (with-current-buffer buffer
      (when (and (derived-mode-p modes) (buffer-file-name))
        (funcall minor-mode value)))))

(defun enable-ro-all-org-mode-buffers ()
  "Enable `buffer-read-only' of all `org-mode' buffers."
  (interactive)
  (set-all-buffers-with-modes #'read-only-mode +1 '(org-mode))
  (message "Enabled `buffer-read-only' of all `org-mode' buffers."))

(defun disable-ro-all-org-mode-buffers ()
  "Disable `buffer-read-only' of all `org-mode' buffers."
  (interactive)
  (set-all-buffers-with-modes #'read-only-mode -1 '(org-mode))
  (message "Disabled `buffer-read-only' of all `org-mode' buffers."))

(defun active-major-modes ()
  "Return a list of active major modes found by iterating over all buffers."
  (let (result)
    (dolist (buffer (buffer-list))
      (with-current-buffer buffer
        (let ((mode major-mode))
          (push mode result))))
    (cl-sort (cl-remove-duplicates result) #'string-lessp)))
#+end_src


* Completion
:PROPERTIES:
:CUSTOM_ID: sec:completion
:END:

[[info:vertico#Top][Vertico (info)]] provides a performant and minimalistic vertical completion UI
based on the default completion system and behaves therefore correctly under all
circumstances.  [[https://cestlaz.github.io/post/using-emacs-80-vertico/][Using Vertico, Marginalia, Consult, and Embark]] links to a video
demonstration.  Vertico integrates well with fully supported complementary
packages to enrich the completion UI:
1. [[info:embark#Top][Embark (info)]] for minibuffer actions with context menus,
2. [[info:marginalia#Top][Marginalia (info)]] for rich annotations in the minibuffer, and
3. [[info:consult#Top][Consult (info)]] for useful search and navigation commands,
where the order is that of [[https://github.com/bdarcus/citar#installation][enhancing citar's experience]] and the configuration
steps below.

Finally, [[https://company-mode.github.io/][company: a modular complete-anything framework for Emacs]] provides
completion in any buffer.

** [[info:vertico#Top][Vertico (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:vertico-configuration
:END:

See the [[yt:hPwDbx--Waw][Vertico extensions for Emacs]] video for an overview.  Listing
[[lst:setup-vertico-mode]] sets up =vertico-mode= without using the
=vertico-directory= extension (less is better!).  Listing
[[lst:prune-file-name-history]] allows to prune non-existing files from the file
name history.

NOTE: Play with =vertico-buffer-mode=, =vertico-flat-mode=, =vertico-grid-mode=,
=vertico-indexed-mode=, =vertico-mouse-mode= (not easy to use with my trackpad),
=vertico-reverse-mode=.

NOTE: The src_emacs-lisp{(describe-function 'savehist-mode)} documentation
explains why it is best to turn on =savehist-mode= in =user-init-file=.

BUG: Adding ~kill-ring~ to ~savehist-additional-variables~ does not save
~kill-ring~ from an Emacs session to the next session, contrary to the
src_emacs-lisp{(describe-variable 'savehist-additional-variables)}
documentation.

#+caption[Setup =vertico-mode=]:
#+caption: Setup =vertico-mode=.
#+name: lst:setup-vertico-mode
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'vertico)
  ;; GAV: Builtin `fido-mode' may fix `find-file' completion when
  ;; using `vertico-directory' functions which confuse `find-file'.
  ;; GAV: Builtin `fido-mode' has more down than up sides: ChatGPT
  ;; bullshits on enhancing `vertico-mode' completion.
  (vertico-mode +1))
#+end_src

#+caption[Prune non-existing files from =file-name-history=]:
#+caption: Prune non-existing files from =file-name-history=.
#+name: lst:prune-file-name-history
#+begin_src emacs-lisp -n :results silent
(defun prune-file-name-history ()
  "Prune non-existing files from `file-name-history'."
  (interactive)
  (let ((old (length file-name-history)) ok)
    (dolist (name file-name-history)
      (when (file-exists-p name)
        (push name ok)))
    (setq file-name-history (nreverse ok))
    (message "Pruned `file-name-history' from `%S' to `%S' files"
             old (length file-name-history))))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Vertico key map bindings]:
#+caption: Vertico key map bindings.
#+name: tab:vertico-keymap-bindings
|-------------------------------+----------------------------------+---------------------|
| command                       | remap                            | keys                |
|-------------------------------+----------------------------------+---------------------|
| vertico-exit                  | exit-minibuffer                  | {{{kbd(C-j)}}}      |
| vertico-exit-input            |                                  | {{{kbd(C-RET)}}}    |
| vertico-first                 | beginning-of-buffer              | {{{kbd(M-<)}}}      |
| vertico-first                 | minibuffer-beginning-of-buffer   | {{{kbd(M-<)}}}      |
| vertico-insert                |                                  | {{{kbd(TAB)}}}      |
| vertico-last                  | end-of-buffer                    | {{{kbd(M->)}}}      |
| vertico-next-group            | forward-paragraph                | {{{kbd(C-<down>)}}} |
| vertico-next                  | next-line-or-history-element     | {{{kbd(<down>)}}}   |
| vertico-next                  | next-line                        | {{{kbd(C-n)}}}      |
| vertico-previous-group        | backward-paragraph               | {{{kbd(C-<up>)}}}   |
| vertico-previous              | previous-line-or-history-element | {{{kbd(<up>)}}}     |
| vertico-previous              | previous-line                    | {{{kbd(C-p)}}}      |
| vertico-save                  | kill-ring-save                   | {{{kbd(M-w)}}}      |
| vertico-scroll-down           | scroll-down-command              | {{{kbd(M-v)}}}      |
| vertico-scroll-up             | scroll-up-command                | {{{kbd(C-v)}}}      |
|-------------------------------+----------------------------------+---------------------|

** [[info:orderless#Top][Orderless (info)]]                                                :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:orderless-configuration
:header-args:emacs-lisp: :tangle no
:END:

 Listing [[lst:configure-orderless]] configures [[info:orderless#Company][orderless for company (info)]].  Note:
*Python editing is orders of magnitude faster after removal of Orderless*.

#+caption[Configure =orderless=]:
#+caption: Configure =orderless=.
#+name: lst:configure-orderless
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'marginalia)
  (with-eval-after-load 'orderless
    (setopt orderless-component-separator " +")

    (defun just-one-face (fn &rest args)
      (let ((orderless-match-faces [completions-common-part]))
        (apply fn args)))

    (advice-add 'company-capf--candidates :around #'just-one-face)))
#+end_src

** [[info:embark#Top][Embark (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:embark-configuration
:END:

Listing [[lst:bind-embark-commands][bind =embark= commands]] binds =embark= commands to the global key map:
1. =embark-act= prompts the user for an action and performs it.  GAV: ~org-mode~
   and ~embark~ do not play together nicely.
2. Except for highlighting of email and web URLs, =embark-dwim= englobes the
   functionality of src_emacs-lisp[:results none]{(find-library "goto-addr")}
   that activates mail and web URLs to turn them into clickable buttons.  Since
   =embark-dwim= acts on a superset of target types, it renders =goto-addr=
   superfluous.  See:
   1. [[info:emacs#Goto Address mode][Goto Address mode (info)]].
   2. [[info:embark#The default action on a target][The default (embark-dwim) action on a target (info)]].
3. =embark-bindings= allows to explore all current command key bindings in the
   minibuffer.
4. The initialization of =prefix-help-command= enables minibuffer help after a
   prefix key (for instance {{{kbd(C-x)}}} or {{{kbd(C-c)}}}) as typing
   {{{kbd(C-x C-h)}}} or {{{kbd(C-c C-h)}}} shows.

#+caption[Bind =embark= commands globally]:
#+caption: Bind =embark= commands globally.
#+name: lst:bind-embark-commands
#+begin_src emacs-lisp -n :results silent
;; GAV: `org-mode' and `embark' do not play together nicely.
;; GAV: `embark' is a dependency of `citar-embark' and `embark-consult'.
(when (ensure-package-installation 'embark-consult)
  (keymap-global-set "C-," #'embark-act)
  (keymap-global-set "C-:" #'embark-dwim)
  (keymap-global-set "C-h B" #'embark-bindings)
  (setq prefix-help-command #'embark-prefix-help-command))
#+end_src

** [[info:marginalia#Top][Marginalia (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:marginalia-configuration
:END:

Listing [[lst:enable-marginalia-mode]] enables =marginalia-mode=.

#+caption[Enable =marginalia-mode=]:
#+caption: Enable =marginalia-mode=.
#+name: lst:enable-marginalia-mode
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'marginalia)
  (marginalia-mode +1))
#+end_src

** [[info:consult#Top][Consult (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:consult-setup
:END:

[[info:consult#Top][Consult (info)]] provides practical commands based on the Emacs minibuffer
completion function [[info:elisp#Minibuffer Completion][completing-read]].  Listing [[lst:bind-consult-commands][bind =consult= commands]] binds
=consult= commands to different key maps.
Consult usage tips are:
1. Add a buffer position to the mark ring by means of {{{kbd(C-SPACE C-SPACE)}}}
   and jump to one of the marks in the ring by means of {{{kbd(M-x
   consult-mark)}}} or {{{kbd(M-g m)}}}.  See [[https://arialdomartini.github.io//emacs-mark-ring][Emacs: Mark Ring]].
2. {{{kbd(M-x consult-org-heading)}}} or {{{kbd(C-c C-h)}}} is an alternative to
   {{{kbd(M-x org-goto)}}} or {{{kbd(C-c C-j)}}}.

#+caption[Bind =consult= commands]:
#+caption: Bind =consult= commands.
#+name: lst:bind-consult-commands
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'consult)
  ;; C-c bindings (current-global-map)
  (keymap-global-set "C-c h" #'consult-history)
  (keymap-global-set "C-c m" #'consult-mode-command)
  ;; C-x bindings (ctl-x-map)
  (keymap-set ctl-x-map "M-:" #'consult-complex-command)
  (keymap-set ctl-x-map "b" #'consult-buffer)
  (keymap-set ctl-x-4-map "b" #'consult-buffer-other-window)
  (keymap-set ctl-x-5-map "b" #'consult-buffer-other-frame)
  (keymap-set ctl-x-r-map "x" #'consult-register)
  (keymap-set ctl-x-r-map "b" #'consult-bookmark)
  ;; M-g bindings (goto-map)
  (keymap-set goto-map "g" #'consult-goto-line)
  (keymap-set goto-map "M-g" #'consult-goto-line)
  (keymap-set goto-map "o" #'consult-outline)
  (keymap-set goto-map "m" #'consult-mark)
  (keymap-set goto-map "k" #'consult-global-mark)
  (keymap-set goto-map "i" #'consult-imenu)
  (keymap-set goto-map "e" #'consult-compile-error)
  (with-eval-after-load 'org
    (keymap-set org-mode-map "C-c C-h" #'consult-org-heading))
  ;; M-s bindings (search-map)
  (keymap-set search-map "g" #'consult-git-grep)
  (keymap-set search-map "f" #'consult-find)
  (keymap-set search-map "k" #'consult-keep-lines)
  (keymap-set search-map "l" #'consult-line)
  (keymap-set search-map "m" #'consult-multi-occur)
  (keymap-set search-map "u" #'consult-focus-lines)
  ;; Other bindings (current-global-map)
  (keymap-global-set "M-y" #'consult-yank-pop))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Configuration specific key bindings]:
#+caption: Configuration specific key-bindings.
#+name: tab:configuration-specific-key-bindings
|-----------------------------+----------------------+--------------------|
| command                     | key map              | keys               |
|-----------------------------+----------------------+--------------------|
| consult-bookmark            | ctl-x-r-keymap       | {{{kbd(C-x r b)}}} |
| consult-buffer-other-frame  | ctl-x-5-keymap       | {{{kbd(C-x 5 b)}}} |
| consult-buffer-other-window | ctl-x-4-keymap       | {{{kbd(C-x 4 b)}}} |
| consult-buffer              | ctl-x-keymap         | {{{kbd(C-x b)}}}   |
| consult-compile-error       | goto-map             | {{{kbd(M-g e)}}}   |
| consult-complex-command     | ctl-x-keymap         | {{{kbd(C-x M-:)}}} |
| consult-find                | search-map           | {{{kbd(M-s f)}}}   |
| consult-focus-lines         | search-map           | {{{kbd(M-s u)}}}   |
| consult-git-grep            | search-map           | {{{kbd(M-s g)}}}   |
| consult-global-mark         | goto-map             | {{{kbd(M-g k)}}}   |
| consult-goto-line           | goto-map             | {{{kbd(M-g M-g)}}} |
| consult-goto-line           | goto-map             | {{{kbd(M-g g)}}}   |
| consult-history             | global-map           | {{{kbd(C-c h)}}}   |
| consult-imenu               | goto-map             | {{{kbd(M-g i)}}}   |
| consult-keep-lines          | search-map           | {{{kbd(M-s k)}}}   |
| consult-line                | search-map           | {{{kbd(M-s l)}}}   |
| consult-mark                | goto-map             | {{{kbd(M-g m)}}}   |
| consult-mode-command        | global-map           | {{{kbd(C-c m)}}}   |
| consult-multi-occur         | search-map           | {{{kbd(M-s m)}}}   |
| consult-org-heading         | org-mode-map         | {{{kbd(C-c C-h)}}} |
| consult-outline             | goto-map             | {{{kbd(M-g o)}}}   |
| consult-register            | ctl-x-r-keymap       | {{{kbd(C-x r x)}}} |
| consult-yank-pop            | global-map           | {{{kbd(M-y)}}}     |
|-----------------------------+----------------------+--------------------|
| elfeed                      | global-map           | {{{kbd(C-x w)}}}   |
| embark-act                  | global-map           | {{{kbd(C-\,)}}}    |
| embark-bindings             | global-map           | {{{kbd(C-h B)}}}   |
| embark-dwim                 | global-map           | {{{kbd(C-:)}}}     |
| iedit-mode                  | global-map           | {{{kbd(C-;)}}}     |
| minibuffer-complete-history | minibuffer-local-map | {{{kbd(C-<tab>)}}} |
| narrow-or-widen-dwim        | ctl-x-keymap         | {{{kbd(C-x C-n)}}} |
| org-agenda                  | global-map           | {{{kbd(C-c a)}}}   |
| org-capture                 | global-map           | {{{kbd(C-c c)}}}   |
| org-cite                    | org-mode-map         | {{{kbd(C-c b)}}}   |
| org-goto                    | org-goto             | {{{kbd(C-c C-j)}}} |
| org-insert-link-global      | global-map           | {{{kbd(C-c C-l)}}} |
| org-narrow-to-table         | ctl-x-keymap         | {{{kbd(C-x n t)}}} |
| org-store-link              | global-map           | {{{kbd(C-c l)}}}   |
|-----------------------------+----------------------+--------------------|

** [[https://company-mode.github.io/][Company (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:company-setup
:END:

[[info:company#Top][Company (info)]] is a modular completion framework and listing [[lst:setup-company]]
configures =company= after ensuring the =company= installation.

#+caption[Setup =company=]:
#+caption: Setup =company=.
#+name: lst:setup-company
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'company)
  ;; https://github.com/purcell/emacs.d/issues/778
  (setopt company-transformers '(company-sort-by-occurrence))
  (add-hook 'LaTeX-mode-hook #'company-mode)
  (add-hook 'org-mode-hook #'company-mode)
  (add-hook 'emacs-lisp-mode-hook #'company-mode)
  (add-hook 'lisp-interaction-mode-hook #'company-mode)
  (add-hook 'lisp-mode-hook #'company-mode)
  (add-hook 'python-mode-hook #'company-mode)
  (add-hook 'ielm-mode-hook #'company-mode)
  (add-hook 'sly-mrepl-mode-hook #'company-mode))
#+end_src

* [[info:emacs#Search][Search and replace (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:search-replace
:END:

** [[info:emacs#Regexp Replace][Regexp Replace (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:regexp-replace
:END:

Executing {{{kbd(M-x replace-regexp)}}} prompts for a regular expression
=REGEXP= and a substitution =NEWSTRING= to replace =REGEXP= with =NEWSTRING=.
The tools in section [[#sec:narrowing][Narrowing]] allow to limit the scope of {{{kbd(M-x
replace-regexp)}}}.  A list pointing to relevant documentation is:
1. [[info:emacs#Regexp Replace][Regexp Replace (info)]] explains how the substitution handles references to
   regular expression groups and lisp expressions.
2. [[info:emacs#Regexps][Syntax of Regular Expressions (info)]] describes regular expression features
   for users.
3. [[info:elisp#Regular Expressions][Emacs Lisp Regular Expressions (info)]] describes regular expression features
   for programmers.
4. [[https://www.emacswiki.org/][Emacs Wiki]] has an article on [[https://www.emacswiki.org/emacs/ReplaceRegexpWithLispExpressions][replacing regexp with lisp expressions]].
Table [[tab:replace-regexp-tranform]] tabulates how to perform example tasks by
means of {{{kbd(M-x replace-regexp)}}} using =(regular-expression transform)=
pairs.

#+attr_latex: :booktabs yes :float table
#+caption[Example =replace-regexp= (regular-expression substitution) pairs]:
#+caption: Example =replace-regexp= (regular-expression substitution) pairs.
#+name: tab:replace-regexp-tranform
| task                        | regular expression              | substitution  |
|-----------------------------+---------------------------------+---------------|
| move dot two digits forward | =0\.\([[:digit:]][[:digit:]]\)= | =0\1.=        |
| move dot two digits forward | =0\.\([0-9][0-9]\)=             | =0\1.=        |
| renumber grep/occur matches | =\(.+:\)=                       | =\,(1+ \#)._= |
|-----------------------------+---------------------------------+---------------|

** [[info:emacs#Incremental Search][Incremental Search (info)]] and [[info:emacs#Other Repeating Search][Other Search and Loop Commands (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:search
:END:

#+caption[Define =multi-occur-in-this-mode=]:
#+caption: Define =multi-occur-in-this-mode=.
#+name: lst:multi-occur-in-this-mode
#+begin_src emacs-lisp -n
;; https://www.masteringemacs.org/article/searching-buffers-occur-mode
(defun get-buffers-matching-mode (mode)
  "Return a list of buffers whose major-mode is equal to MODE."
  (let ((buffer-mode-matches '()))
    (dolist (buf (buffer-list))
      (with-current-buffer buf
        (when (eq mode major-mode)
          (push buf buffer-mode-matches))))
    buffer-mode-matches))

(defun multi-occur-in-this-mode ()
  "Show all lines matching REGEXP in buffers with this major mode."
  (interactive)
  (multi-occur
   (get-buffers-matching-mode major-mode)
   (car (occur-read-primary-args))))
#+end_src

#+caption[Use =consult-line= from =isearch=]:
#+caption: Use =consult-line= from =isearch=.
#+name: lst:consult-line-from-isearch
#+begin_src emacs-lisp -n :results silent
;; https://blog.chmouel.com/posts/emacs-isearch/
(when (package-installed-p 'consult)
  (defun consult-line-from-isearch ()
    "Invoke `consult-line' from isearch."
    (interactive)
    (let ((query (if isearch-regexp
                     isearch-string
                   (regexp-quote isearch-string))))
      (isearch-update-ring isearch-string isearch-regexp)
      (let (search-nonincremental-instead)
        (ignore-errors (isearch-done t t)))
      (consult-line query)))

  (keymap-set isearch-mode-map "C-l" #'consult-line-from-isearch))
#+end_src

#+caption[Use =occur= and =project-find-regexp= from =isearch=]:
#+caption: Use =occur= and =project-find-regexp= from =isearch=.
#+name: lst:occur-and-project-find-regexp-from-isearch
#+begin_src emacs-lisp -n :results silent
;; https://blog.chmouel.com/posts/emacs-isearch/
(defun occur-from-isearch ()
  "Invoke `occur' from isearch."
  (interactive)
  (let ((query (if isearch-regexp
                   isearch-string
                 (regexp-quote isearch-string))))
    (isearch-update-ring isearch-string isearch-regexp)
    (let (search-nonincremental-instead)
      (ignore-errors (isearch-done t t)))
    (occur query)))

(defun project-find-regexp-from-isearch ()
  "Invoke `project-find-regexp' from isearch."
  (interactive)
  (let ((query (if isearch-regexp
                   isearch-string
                 (regexp-quote isearch-string))))
    (isearch-update-ring isearch-string isearch-regexp)
    (let (search-nonincremental-instead)
      (ignore-errors (isearch-done t t)))
    (project-find-regexp query)))

(keymap-set isearch-mode-map "C-o" #'occur-from-isearch)
(keymap-set isearch-mode-map "C-f" #'project-find-regexp-from-isearch)
#+end_src

** [[https://www.genivia.com/get-ugrep.html][Ugrep]]
:PROPERTIES:
:CUSTOM_ID: sec:ugrep
:END:

[[https://www.genivia.com/get-ugrep.html][Ugrep]] is an ultra fast grep with interactive query UI and fuzzy search.  The
pages [[https://github.com/Genivia/ugrep#emacs][Using ugrep within Emacs]] and [[https://manueluberti.eu/emacs/2022/08/07/emacs-ugrep/][Ugrep in Emacs]] show how to make Emacs use it
with [[info:emacs#Grep Searching][lgrep]] and [[info:emacs#Xref][xref]].  Listing [[lst:set-grep+xref-options][set =grep= and =xref= options]] shows my
implementation of the suggestions on those pages.  *To do*:
1. None of the commands listed in [[info:emacs#Grep Searching][Searching with Grep under Emacs (info)]]
   works on my system with the exception of ~lgrep~ when using [[https://www.genivia.com/get-ugrep.html][ugrep]].
2. None of the ~grep~, ~agrep~, ~egrep~, ~fgrep~, and ~glimpse~ builtins listed
   in [[info:eshell#Built-ins][Eshell builtins (info)]] works.

#+caption[Set =grep= and =xref= options to use =ugrep= when available]:
#+caption: Set =grep= and =xref= options to use =ugrep= when available.
#+name: lst:set-grep+xref-options
#+begin_src emacs-lisp -n :results silent
(when (executable-find "ugrep")
  (with-eval-after-load 'grep
    (setopt grep-template (string-join '("ugrep"
                                         "--color=always"
                                         "--decompress"
                                         "--ignore-binary"
                                         "--ignore-case"
                                         "--include=\"<F>\""
                                         "--line-number"
                                         "--null"
                                         "--recursive"
                                         "--regexp=<R>")
                                       " ")
            grep-command "ugrep --color=always --null -nH -e "
            grep-use-null-device nil))
  (with-eval-after-load 'xref
    (setopt
     xref-search-program 'ugrep
     xref-search-program-alist
     `((grep . "xargs -0 grep <C> --null -snHE -e <R>")
       (ripgrep . ,(concat "xargs -0 rg <C> --null -nH"
                           " --no-heading --no-messages -g '!*/' -e <R>"))
       (ugrep . "xargs -0 ugrep <C> --null -ns -e <R>")))))
#+end_src

** [[https://github.com/mattiase/xr#readme][XR - Emacs regexp parser and analyzer]]
:PROPERTIES:
:CUSTOM_ID: sec:ensure-xr-installation
:END:

[[https://github.com/mattiase/xr#readme][XR]] converts Emacs regular expressions to the structured =rx= form, thus being an
inverse of =rx=. It can also find mistakes and questionable constructs inside
regexp strings.

#+caption[Ensure =xr= installation]:
#+caption: Ensure =xr= installation.
#+name: lst:ensure-xr-installation
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'xr)
#+end_src

* [[info:emacs#Version Control][Version Control (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:version-control
:END:

** [[info:ediff#Top][Ediff (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:ediff
:END:

Video links to complete the [[info:ediff#Top][ediff (info)]] manual are:
1. [[https://www.youtube.com/watch?v=6ZWp05OW1c0][Emergency Emacs]].
2. [[https://protesilaos.com/codelog/2020-04-10-emacs-smerge-ediff/][Use =smerge= and =ediff= to resolve file conflicts]].
Listing [[lst:setup-ediff]] configures =ediff= to display all its buffers in a
single frame and to make all text visible prior to ediffing Org buffers.

#+caption[Setup =ediff=]:
#+caption: Setup =ediff=.
#+name: lst:setup-ediff
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ediff-wind
  (when (fboundp 'ediff-setup-windows-plain)
    (setopt ediff-merge-split-window-function #'split-window-horizontally
            ediff-split-window-function #'split-window-horizontally
            ediff-window-setup-function #'ediff-setup-windows-plain)))
(with-eval-after-load 'org
  ;; https://github.com/oantolin/emacs-config#readme
  (add-hook 'org-mode-hook
            (defun ediff-with-org-show-all ()
              "Expand all headings prior to ediffing org buffers."
              (add-hook 'ediff-prepare-buffer-hook #'org-fold-show-all nil t))))
#+end_src

** [[https://git-scm.com/book/en/v2][Git]]
:PROPERTIES:
:CUSTOM_ID: sec:git
:END:

*** [[info:magit#Top][Magit (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:magit
:END:

[[info:magit#Top][Magit (info)]] is an Emacs interface to the version control system [[https://git-scm.com/book/en/v2][Git]] and the
snippet [[lst:ensure-magit-installation][below]] ensures its installation.  Magit usage tips are:
1. [[https://stackoverflow.com/questions/tagged/magit?tab=Votes][Most upvoted Magit questions on Stack Overflow]].
2. [[https://stackoverflow.com/a/33644270][Abort an active rebase]] by pressing {{{kbd(r a)}}}.
I still have to understand [[info:magit#Pushing][Magit pushing (info)]] and to figure out how to use
src_emacs-lisp{(magit-push-current-to-pushremote)} or
src_emacs-lisp{(magit-push-current-to-upstream)}.

#+caption[Ensure =Magit= installation]:
#+caption: Ensure =Magit= installation
#+name: lst:ensure-magit-installation
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'magit)
#+end_src

*** Github quick setup
:PROPERTIES:
:CUSTOM_ID: sec:github-quick-setup
:END:

#+caption[Make a new repository on the command line]:
#+caption: Make a new repository on the command line.
#+name: lst:make-new-git-repo
#+begin_src shell -n :eval never
echo "# oglot" >> README.md
git init
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin git@github.com:gav451/oglot.git
git push -u origin main
#+end_src

#+caption[Push an old git repository on the command line]:
#+caption: Push an old git repository on the command line.
#+name: lst:push-old-git-repo
#+begin_src shell -n :eval never
git remote add origin git@github.com:gav451/oglot.git
git branch -M main
git push -u origin main
#+end_src

*** Learn git
:PROPERTIES:
:CUSTOM_ID: sec:learn-git
:END:

Useful [[https://git-scm.com/book/en/v2][Git]] links are:
- [[https://sentry.io/answers/abort-a-merge-in-git/][Abort a merge in Git]]
- [[https://sentry.io/answers/change-the-uri-for-a-git-remote/][Change the URI for a Git remote]]
- [[https://sentry.io/answers/check-out-a-remote-branch-in-git/][Check out a remote branch in Git]]
- [[https://sentry.io/answers/clone-a-git-repository-to-a-specific-folder/][Clone a Git repository to a specific folder]]
- [[https://sentry.io/answers/clone-a-specific-git-repository-branch/][Clone a specific Git repository branch]]
- [[https://sentry.io/answers/create-a-new-git-branch-from-an-existing-branch/][Create a new Git branch from an existing branch]]
- [[https://sentry.io/answers/create-a-remote-branch-in-git/][Create a remote branch in Git]]
- [[https://sentry.io/answers/delete-a-commit-from-a-branch-in-git/][Delete a commit from a branch in Git]]
- [[https://sentry.io/answers/delete-a-file-from-a-git-repository/][Delete a file from a Git repository]]
- [[https://sentry.io/answers/delete-a-git-branch-locally-and-remotely/][Delete a Git branch locally and remotely]]
- [[https://sentry.io/answers/determine-the-origin-of-a-cloned-git-repository/][Determine the origin of a cloned Git repository]]
- [[https://sentry.io/answers/undo-the-most-recent-local-git-commits/][Undo the most recent local Git commits]]

*** [[https://www.theserverside.com/blog/Coffee-Talk-Java-News-Stories-and-Opinions/git-push-new-branch-remote-github-gitlab-upstream-example][List all Git branches]]
:PROPERTIES:
:CUSTOM_ID: sec:list-all-git-branches
:END:

#+caption[List all =git= branches]:
#+caption: List all =git= branches.
#+name: lst:list-all-git-branches
#+begin_src shell -n :exports both :results verbatim
git -C ~/VCS/oglot branch -a
#+end_src

#+RESULTS: lst:list-all-git-branches
: * main
:   remotes/origin/main

* Reading
:PROPERTIES:
:CUSTOM_ID: sec:reading
:END:

** Reading [[https://en.wikipedia.org/wiki/DjVu][DjVu]] files
:PROPERTIES:
:CUSTOM_ID: sec:reading-djvu-files
:END:

[[info:emacs#Document View][Document View (info)]] allows to read [[https://en.wikipedia.org/wiki/DjVu][DjVu]] files on condition that it can use the
command line [[https://en.wikipedia.org/wiki/DjVu][DjVu]] decoder =ddjvu= from the [[http://djvu.sourceforge.net/][DjVuLibre]] utilities as shown by the
code of src_emacs-lisp{(find-function 'doc-view-djvu->tiff-converter-ddjvu)}.
Use {{{kbd(+)}}} or {{{kbd(-)}}} to enlarge or shrink what =doc-view-mode=
displays and use {{{kbd(SPC)}}} or {{{kbd(S-SPC)}}} to scroll down or up through
when pages are larger than the =doc-view-mode= window.

** Reading EPUB files
:PROPERTIES:
:CUSTOM_ID: sec:reading-epub-files
:END:

The package [[https://depp.brause.cc/nov.el/][nov.el]] provides a major mode for reading EPUB files in Emacs.
Listing [[lst:configure-nov]] configures [[https://depp.brause.cc/nov.el/][nov.el]].

#+caption[Configure =nov=]:
#+caption: Configure =nov=.
#+name: lst:configure-nov
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'nov)
  (add-to-list 'auto-mode-alist `(,(rx ".epub" eos) . nov-mode)))
#+end_src

** Reading PDF files
:PROPERTIES:
:CUSTOM_ID: sec:reading-pdf-files
:END:

The [[https://github.com/vedang/pdf-tools][pdf-tools]] package exploits the [[https://github.com/freedesktop/poppler][poppler]] library to render and to let you
annotate [[https://en.wikipedia.org/wiki/PDF][PDF]] files.  It also exploits the [[https://wiki.contextgarden.net/SyncTeX][SyncTeX]] library to link anchors in [[https://en.wikipedia.org/wiki/PDF][PDF]]
files produced with LaTeX to the original LaTeX sources.  In order to use
[[https://github.com/vedang/pdf-tools][pdf-tools]], you have to type {{{kbd(M-x pdf-tools-install)}}} after installation
of [[https://github.com/vedang/pdf-tools][pdf-tools]] from [[https://melpa.org/][MELPA]] or after each update of [[https://github.com/freedesktop/poppler][poppler]] to build or rebuild the
=epdfinfo= executable that serves the [[https://en.wikipedia.org/wiki/PDF][PDF]] files to Emacs.  Table
[[tab:pdf-view-mode-commands-and-bindings]] lists important local map key bindings
in ~pdf-view-mode~.  Note: ~image-save~ saves the page under point to a ~png~
file.

#+caption[Setup =pdf-tools=]:
#+caption: Setup =pdf-tools=.
#+name: lst:setup-pdf-tools
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'pdf-tools)
  ;; Use `pdf-loader-install' for faster startup than with `pdf-tools-install'.
  (pdf-loader-install)

  (with-eval-after-load 'pdf-view
    (setopt pdf-view-display-size 'fit-page
            pdf-view-use-scaling (eq system-type 'darwin))))
#+end_src


#+attr_latex: :booktabs yes :float table
#+caption[Commands with local key bindings in ~pdf-view-mode~]:
#+caption: Commands with local key bindings in ~pdf-view-mode~.
#+name: tab:pdf-view-mode-commands-and-bindings
|---------------------------------+----------------|
| command                         | key binding    |
|---------------------------------+----------------|
| *image-save*                    | {{{kbd(i o)}}} |
| *pdf-outline*                   | {{{kbd(o)}}}   |
| *pdf-view-fit-height-to-window* | {{{kbd(H)}}}   |
| *pdf-view-fit-width-to-window*  | {{{kbd(W)}}}   |
|---------------------------------+----------------|

** Reading outline files
:PROPERTIES:
:CUSTOM_ID: sec:reading-outline-files
:END:

#+caption[Enable ~read-only-mode~ for some files in ~outline-mode~]:
#+caption: Enable ~read-only-mode~ for some files in ~outline-mode~.
#+name: lst:maybe-read-only-in-outline-mode
#+begin_src emacs-lisp -n :results silent
(defun maybe-read-only-in-outline-mode ()
  ;; GAV: Should be a toplevel function to call `message' here.
  (let ((fnsd (buffer-file-name)))
    ;; GAV: `fnsd' is nil during Org export to LaTeX.
    (when fnsd
      (setq fnsd (file-name-nondirectory fnsd))
      ;; These are files from the EMACS and ORG git repositories.
      (when (member fnsd '("EGLOT-NEWS" "NEWS" "ORG-NEWS" "PROBLEMS"
                           "org.org" "org-guide.org" "org-manual.org"))
        (message "Visit `%s' in `read-only-mode'" fnsd)
        (read-only-mode +1)))))
(add-hook 'outline-mode-hook #'maybe-read-only-in-outline-mode)
#+end_src

* Writing
:PROPERTIES:
:CUSTOM_ID: sec:writing
:END:

** Writing LaTeX files
:PROPERTIES:
:CUSTOM_ID: sec:writing-latex-files
:END:

Loading =tex.el= immediately instead of lazily ensures proper initialization of
[[https://en.wikipedia.org/wiki/AUCTeX][AUCTeX]].  In particular, the ~TeX-master~ safe local variable in the =tex.el=
elisp library file has no autoload cookie.  Without prior loading of =tex.el=,
Emacs will complain that ~TeX-master~ is no safe local variable in case it reads
a LaTeX file that sets ~TeX-master~.  The list below summarizes the main [[https://en.wikipedia.org/wiki/AUCTeX][AUCTeX]]
configuration objectives:
1. Listing [[lst:set-tex-options]] ensures installation of [[https://en.wikipedia.org/wiki/AUCTeX][AUCTeX]] and initializes
   [[https://en.wikipedia.org/wiki/AUCTeX][AUCTeX]] properly for =LuaTeX= or =LuaLaTeX=.
2. Listing [[lst:set-tex-options]] also enables *indenting between square brackets*
   which is a recent feature.
3. Listing [[lst:update-lualatex-opentype-font-name-database]] defines a function to
   update the =OpenType Font= name database for =LuaLaTeX= when the output of
   =LuaLaTeX= shows missing fonts.
4. Listing [[lst:set-bibtex-options]] configures the Emacs =bibtex= library to use
   the LaTeX =BiBTeX= dialect for backwards compatibility.
5. Listing [[lst:set-font-latex-options]] disables font scaling of section titles.
6. Listing [[lst:set-latex-options]] configures =latex= for a full featured
   =LaTeX-section-command=.

#+caption[Ensure =AUCTeX= installation and set =TeX= option]:
#+caption: Ensure =AUCTeX= installation and set =TeX= option.
#+name: lst:set-tex-options
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'auctex)
  ;; Use `require' to make `TeX-master' a safe local variable.
  (when (require 'tex nil 'noerror)
    (setopt
     TeX-auto-save t
     TeX-engine 'luatex
     TeX-indent-close-delimiters "]"
     TeX-indent-open-delimiters "["
     TeX-parse-self t
     ;; Disable `TeX-electric-math' to prevent collisions with `smartparens'.
     TeX-electric-math nil)))
#+end_src

#+caption[Update the =LuaLaTeX OpenType Font=  name database]:
#+caption: Update the =LuaLaTeX= =OpenType Font= name database.
#+name: lst:update-lualatex-opentype-font-name-database
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (defun update-lualatex-opentype-font-name-database ()
    "Update the \"OpenType Font\" name database for \"LuaLaTeX\"."
    (interactive)
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code
         "luaotfload-tool" "-vv" "--update" "--force")
      (if (= 0 exit-code)
          (message "%s" (string-trim output))
        (error "%s" (string-trim output))))))
#+end_src

#+caption[Set =bibtex= options]:
#+caption: Set =bibtex= options.
#+name: lst:set-bibtex-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'bibtex
  (setopt bibtex-dialect 'BibTeX))
#+end_src

#+caption[Set =font-latex= options]:
#+caption: Set =font-latex= options.
#+name: lst:set-font-latex-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'font-latex
  (setopt font-latex-fontify-sectioning 1.0))
#+end_src

#+caption[Set =latex= options]:
#+caption: Set =latex= options.
#+name: lst:set-latex-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'latex
  (setopt LaTeX-electric-left-right-brace t
          LaTeX-section-hook '(LaTeX-section-heading
                               LaTeX-section-title
                               LaTeX-section-toc
                               LaTeX-section-section
                               LaTeX-section-label)))
#+end_src

** Writing [[https://www.markdownguide.org/][Markdown]] files
:PROPERTIES:
:CUSTOM_ID: sec:writing-markdown-files
:END:

#+caption[Configure =markdown-mode=]:
#+caption: Configure =markdown-mode=.
#+name: lst:configure-markdown-mode
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'markdown-mode) t)
#+end_src

** Writing [[info:org#Top][Org (info)]] files and [[info:org#Activation][Org activation (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:writing-org-files
:END:

Listing [[lst:bind-org-commands]] activates [[info:org#Top][Org (info)]] by means of global key
bindings.

#+caption[Bind =Org= commands globally]:
#+caption: Bind =Org= commands globally.
#+name: lst:bind-org-commands
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (global-set-key (kbd "C-c a") #'org-agenda)
  (global-set-key (kbd "C-c c") #'org-capture)
  (global-set-key (kbd "C-c l") #'org-store-link))
#+end_src

Links to Org-mode videos are:
1. [[yt:o6rE18Mxu9U][Analyze Your Time with Org Mode Clocktables]]
2. [[yt:EgOBBiomfGo][Basic Task Management with Org: Checklists, TODOs, and Org-Agenda]]
3. [[yt:oJTwQvgfgMM][Emacs Org-mode: a system for note-taking and project planning]]
4. [[yt:SzA2YODtgK4][Getting Started With Org Mode]]
5. [[yt:zqAYHWv36X0][Org Mode Time and Task Tools]]

*** Setup Org
:PROPERTIES:
:CUSTOM_ID: sec:setup-org
:ID:       0D725DA1-7431-40BD-85FF-EFF4F7E4EC95
:END:

I have split the initial [[https://orgmode.org/][Org-mode]] setup over twelve listings.  Here, follows a
list detailing and motivating each listing:
1. Listing [[lst:set-org-options]] handles basic [[https://orgmode.org/][Org-mode]] options.
2. Listing [[lst:org-capture-templates]] initializes a simple capture template.
3. Listing [[lst:setup-org-babel]] sets ~ob-core~, ~ob-latex~, and ~ob-lisp~ options.
   See [[info:org#Working with Source Code][working with source code (info)]] for Org Babel information.
4. Listing [[lst:looking-at-org-id]] enables recent ~org-id~ features.
5. Listing [[lst:setup-org-mode-map-1]] and [[lst:setup-org-mode-map-2]] extend the
   =org-mode-map= with useful key-bindings.
6. Listing [[lst:setup-org-src]] facilitates [[info:org#Editing Source Code][editing source code blocks]], and it
   provides functions to change the indentation of all =org-src-mode= blocks.
7. Listing [[lst:setup-ob-python]] allows to pretty-print Python session source
   block values with [[https://github.com/psf/black#readme][black]] instead of [[https://docs.python.org/3/library/pprint.html][pprint]].  This snippet may break in the
   future, because it sets =org-babel-python--def-format-value= which is a
   constant declared "private" by two dashes in its name!
8. Listing [[lst:set-org-export-options]] selects the =non-intrusive= expert user
   interface for export dispatching.
9. Listing [[lst:setup-org-for-lualatex-export]] and
   [[lst:set-ox-latex-options-for-lualatex-export]] configure [[https://orgmode.org/][Org-mode]] to generate
   output for the LuaLaTeX compiler.
10. Listing [[lst:setup-org-latex-classes]] defines [[info:org#LaTeXspecificexportsettings][org-latex-classes (info)]] for
    backward compatibility.  For an explanation of the code in listing
    [[lst:setup-org-latex-classes]], type {{{kbd(C-h v org-latex-classes)}}}.

#+caption[Set basic =Org= options]:
#+caption: Set basic =Org= options.
#+name: lst:set-org-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org
  (setopt
   org-agenda-files '("gerard.org")
   org-agenda-include-diary t
   org-babel-load-languages `((calc . t)
                              (dot . ,(fboundp 'grapviz-dot-mode))
                              (emacs-lisp . t)
                              (eshell . t)
                              (fortran . t)
                              (gnuplot . ,(fboundp 'gnuplot-mode))
                              (latex . t)
                              (lilypond . ,(fboundp 'lilypond-mode))
                              (lisp . t)
                              (lua . ,(fboundp 'lua-mode))
                              (org . t)
                              (perl . t)
                              ;; Beware of circular Python dependencies.
                              (python . t)
                              (ruby . ,(fboundp 'ruby-mode))
                              (shell . t))
   org-directory "~/org"
   org-export-backends '(ascii beamer html icalendar latex md odt texinfo)
   org-file-apps '((auto-mode . emacs)
                   (directory . emacs)
                   ("\\.mm\\'" . default)
                   ("\\.x?html?\\'" . default)
                   ("\\.pdf\\'" . emacs))
   ;; Set `org-link-descriptive' interactively by `org-toggle-link-display'.
   org-link-descriptive t
   org-link-file-path-type 'adaptive
   org-modules (list 'ol-bibtex 'ol-doi 'ol-eww 'ol-info
                     'org-id 'org-protocol 'org-tempo)
   org-use-property-inheritance t))
#+end_src

#+caption[Setup =org-capture-templates=]:
#+caption: Setup =org-capture-templates=.
#+name: lst:org-capture-templates
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org-capture
  (setopt org-capture-templates
          '(("f" "Flat capture database" entry (file "flat.org")
             "* %^{Prompt}t %?
%a"))))
#+end_src

#+caption[Set =org-babel= options]:
#+caption: Set =org-babel= options.
#+name: lst:setup-org-babel
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ob-core
  (setopt org-confirm-babel-evaluate nil))

(with-eval-after-load 'ob-latex
  (setopt org-babel-latex-preamble
          (lambda (_)
            "\\documentclass[preview]{standalone}\n")))

(with-eval-after-load 'ob-lisp
  (when (package-installed-p 'sly)
    (setopt org-babel-lisp-eval-fn #'sly-eval)))
#+end_src

#+caption[Looking at =org-id=]:
#+caption: Looking at =org-id=.
#+name: lst:looking-at-org-id
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org-id
  (setopt org-id-link-to-org-use-id t
          org-id-track-globally t)
  ;; https://stackoverflow.com/a/16247032 answers
  ;; "How to assign IDs to all entries in a buffer."
  (defun org-id-add-ids-to-headlines-in-buffer ()
    "Add slowly ID properties to all headlines without such an ID property.
Undo this by means of `org-delete-property-globally'."
    (interactive)
    (org-map-entries #'org-id-get-create)))
#+end_src

#+caption[Setup =org-mode-map= 1]:
#+caption: Setup =org-mode-map= 1.
#+name: lst:setup-org-mode-map-1
#+begin_src emacs-lisp -n :results silent
;; From: "Nicolas Richard" <theonewiththeevillook@yahoo.fr>
;; Date: Fri, 08 Mar 2013 16:23:02 +0100	[thread overview]
;; Message-ID: <87vc913oh5.fsf@yahoo.fr> (raw)
(defun org-electric-dollar ()
  "When called once, insert \\(\\) and leave point in between.
When called twice, replace the previously inserted \\(\\) by one $."
  (interactive)
  (if (and (looking-at "\\\\)") (looking-back "\\\\(" (- (point) 2)))
      (progn (delete-char 2) (delete-char -2) (insert "$"))
    (insert "\\(\\)")
    (backward-char 2)))

(with-eval-after-load 'org
  (setopt org-return-follows-link t)
  (keymap-set org-mode-map "$" #'org-electric-dollar)
  (keymap-set org-mode-map "M-q" #'org-fill-paragraph))
#+end_src

#+caption[Setup =org-mode-map= 2]:
#+caption: Setup =org-mode-map= 2.
#+name: lst:setup-org-mode-map-2
#+begin_src emacs-lisp -n :results silent
;; Stolen from `org-insert-structure-template'.
;; Note: `org-tempo' does not require `tempo' at all.
(defcustom org-insert-source-block-defaults
  '("calc -n :results silent"
    "emacs-lisp -n :results silent"
    "latex -n"
    "lisp -n :results silent :package :cs325-user"
    "org -n"
    "python -i -n :results silent")
  "Default values for `org-insert-source-block'."
  :group 'org
  :type '(repeat string))

(defun org-insert-source-block ()
  "Insert a source block #+begin_src/SPEC/BODY/#+end_src.
Prompt for the source block SPEC.  With an active region, the
region becomes the block BODY.  Otherwise, insert an empty block."
  (interactive)
  (let* ((spec (completing-read
                "Block spec: " org-insert-source-block-defaults nil 'confirm))
         (region? (use-region-p))
         (region-start (and region? (region-beginning)))
         (region-end (and region? (copy-marker (region-end)))))
    (when region? (goto-char region-start))
    (let ((column (current-indentation)))
      (if (save-excursion (skip-chars-backward " \t") (bolp))
          (forward-line 0)
        (insert "\n"))
      (save-excursion
        (indent-to column)
        (insert (format "#+begin_src %s\n" spec))
        (when region?
          (org-escape-code-in-region (point) region-end)
          (goto-char region-end)
          (skip-chars-backward " \n\t\r")
          (end-of-line))
        (unless (bolp) (insert "\n"))
        (indent-to column)
        (insert "#+end_src")
        (if (looking-at "[ \t]*$") (replace-match "") (insert "\n"))
        (when (and (eobp) (not (bolp))) (insert "\n")))
      (end-of-line))))

(with-eval-after-load 'org
  (keymap-set org-mode-map "C-c C-;" #'org-insert-source-block))
#+end_src

#+caption[Setup =org-src=]:
#+caption: Setup =org-src=.
#+name: lst:setup-org-src
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org-src
  ;; https://list.orgmode.org/c3cc4ff1fcfb3bc741df89a3f45be30e@posteo.net/
  (setopt org-edit-src-content-indentation 0
          org-src-preserve-indentation nil
          org-src-window-setup 'current-window)

  (defun org-left-shift-block ()
    "Left-shift the block at point using `org-indent-block'."
    (interactive)
    (let ((org-adapt-indentation nil)
          (org-edit-src-content-indentation 0)
          (org-src-preserve-indentation nil))
      (org-indent-block)))

  (defun org-right-shift-block (&optional arg)
    "Right-shift the block at point 4 spaces.
With prefix argument ARG, prompt for the number of spaces."
    (interactive "P")
    (let ((spaces 4)
          (start (org-babel-where-is-src-block-head)))
      (if (not start) (message "Not at block")
        (when arg
          (setq spaces (read-number "Number of spaces: ")))
        ;; The `SUBEXP' of the block body is 5.
        (goto-char (match-end 5))
        (forward-line -1)
        (string-insert-rectangle
         (match-beginning 5) (point) (make-string spaces ?\s)))))

  (defun zero-all-org-src-blocks-indentation ()
    "Remove the indentation of all `org-src-mode' blocks without `-i' switch."
    (interactive)
    (when (derived-mode-p 'org-mode)
      (save-excursion
        (org-babel-map-src-blocks
            nil
          (unless (or (string-match "-i " switches)
                      (string-match (rx (or bos bol) graph) body))
            (when-let ((new (with-temp-buffer
                              (insert body)
                              (org-do-remove-indentation)
                              (buffer-string))))
              (goto-char beg-body)
              (delete-region beg-body end-body)
              (insert new))))))))
#+end_src

#+caption[Setup =ob-python=]:
#+caption: Setup =ob-python=.  This snippet may break in the future!
#+name: lst:setup-ob-python
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ob-python
  (setq org-babel-python--def-format-value "\
def __org_babel_python_format_value(result, result_file, result_params):
    with open(result_file, 'w') as f:
        if 'graphics' in result_params:
            result.savefig(result_file)
        elif 'pp' in result_params:
            import black
            f.write(black.format_str(repr(result), mode=black.Mode()))
        elif 'list' in result_params and isinstance(result, dict):
            f.write(str(['{} :: {}'.format(k, v) for k, v in result.items()]))
        else:
            if not set(result_params).intersection(\
['scalar', 'verbatim', 'raw']):
                def dict2table(res):
                    if isinstance(res, dict):
                        return [(k, dict2table(v)) for k, v in res.items()]
                    elif isinstance(res, list) or isinstance(res, tuple):
                        return [dict2table(x) for x in res]
                    else:
                        return res
                if 'table' in result_params:
                    result = dict2table(result)
                try:
                    import pandas
                except ImportError:
                    pass
                else:
                    if isinstance(result, pandas.DataFrame) and 'table' in result_params:
                        result = [[result.index.name or ''] + list(result.columns)] + \
[None] + [[i] + list(row) for i, row in result.iterrows()]
                    elif isinstance(result, pandas.Series) and 'table' in result_params:
                        result = list(result.items())
                try:
                    import numpy
                except ImportError:
                    pass
                else:
                    if isinstance(result, numpy.ndarray):
                        if 'table' in result_params:
                            result = result.tolist()
                        else:
                            result = repr(result)
            f.write(str(result))"))
#+end_src

#+caption[Set =org-export= options]:
#+caption: Set =org-export= options.
#+name: lst:set-org-export-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ox
  (setopt org-export-dispatch-use-expert-ui t))
#+end_src

#+caption[Setup =org= for export to LuaLaTeX]:
#+caption: Setup =org= for export to LuaLaTeX.
#+name: lst:setup-org-for-lualatex-export
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org
  ;; https://list.orgmode.org/87o84fd4oi.fsf@posteo.net/
  (add-to-list
   'org-preview-latex-process-alist
   '(luamagick
     :programs ("lualatex" "convert")
     :description "pdf > png"
     :message "you need to install lualatex and imagemagick."
     :image-input-type "pdf"
     :image-output-type "png"
     :image-size-adjust (1.0 . 1.0)
     :post-clean nil
     :latex-header nil
     :latex-compiler
     ("lualatex -interaction nonstopmode -output-directory %o %f")
     :image-converter
     ("convert -density %D -trim -antialias %f -quality 100 %O")))
  (setopt
   org-preview-latex-default-process 'luamagick
   org-latex-default-packages-alist '(("" "fontspec" t ("lualatex"))
                                      ("AUTO" "inputenc" t ("pdflatex"))
                                      ("T1" "fontenc" t ("pdflatex"))
                                      ("" "graphicx" t)
                                      ("" "longtable" nil)
                                      ("" "wrapfig" nil)
                                      ("" "rotating" nil)
                                      ("normalem" "ulem" t)
                                      ("" "amsmath" t)
                                      ("" "amssymb" t)
                                      ("" "capt-of" nil)
                                      ("" "hyperref" nil))))
#+end_src

#+caption[Set =ox-latex= options for export to LuaLaTeX]:
#+caption: Set =ox-latex= options for export to LuaLaTeX.
#+name: lst:set-ox-latex-options-for-lualatex-export
#+begin_src emacs-lisp -n :results silent
(when (require 'ox-latex nil 'noerror) ;; To use the safe file local variables!
  (setopt
   org-latex-compiler "lualatex"
   org-latex-compiler-file-string
   "%% -*- LaTeX -*-\n%% Intended LaTeX compiler: %s\n"
   org-latex-hyperref-template "\\hypersetup{
  pdfauthor={%a},
  pdftitle={%t},
  pdfkeywords={%k},
  pdfsubject={%d},
  pdfcreator={%c},
  pdflang={%L},
  citecolor=blue,
  colorlinks=true,
  filecolor=blue,
  hyperfootnotes=false,
  linkcolor=blue,
  unicode=true,
  urlcolor=blue,
}\n"
   org-latex-minted-langs '((cc "c++")
                            (conf "text")
                            (cperl "perl")
                            (diff "diff")
                            (shell-script "bash")
                            (json "json")
                            (org "text")
                            (toml "toml"))
   org-latex-minted-options '(("bgcolor" "LightGoldenrodYellow"))
   org-latex-logfiles-extensions
   (cl-union '("lof" "lot") org-latex-logfiles-extensions :test #'equal)
   ;; https://tecosaur.github.io/emacs-config/#compiling
   org-latex-pdf-process (list (concat "latexmk -f -pdf -%latex"
                                       " -interaction=nonstopmode"
                                       " -shell-escape -outdir=%o %f"))
   org-latex-prefer-user-labels t)

  (put 'org-latex-toc-command 'safe-local-variable 'stringp))
#+end_src

#+caption[Setup =org-latex-classes= for backwards compatibility]:
#+caption: Setup =org-latex-classes= for backwards compatibility.
#+name: lst:setup-org-latex-classes
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ox-latex
  (mapc (function (lambda (element)
                    (add-to-list 'org-latex-classes element)))
        (nreverse
         (quote (("elsarticle-1+2+3"	; Elsevier journals
                  "\\documentclass{elsarticle}
[NO-DEFAULT-PACKAGES]
[PACKAGES]
[EXTRA]"
                  ("\\section{%s}" . "\\section*{%s}")
                  ("\\subsection{%s}" . "\\subsection*{%s}")
                  ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
                  ("\\paragraph{%s}" . "\\paragraph*{%s}")
                  ("\\subparagraph{%s}" . "\\subparagraph*{%s}"))
                 ("article-1+2+3"
                  "\\documentclass{article}
[NO-DEFAULT-PACKAGES]
[PACKAGES]
[EXTRA]"
                  ("\\section{%s}" . "\\section*{%s}")
                  ("\\subsection{%s}" . "\\subsection*{%s}")
                  ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
                  ("\\paragraph{%s}" . "\\paragraph*{%s}")
                  ("\\subparagraph{%s}" . "\\subparagraph*{%s}"))
                 ("report-1+2+3"
                  "\\documentclass[11pt]{report}
[NO-DEFAULT-PACKAGES]
[PACKAGES]
[EXTRA]"
                  ("\\part{%s}" . "\\part*{%s}")
                  ("\\chapter{%s}" . "\\chapter*{%s}")
                  ("\\section{%s}" . "\\section*{%s}")
                  ("\\subsection{%s}" . "\\subsection*{%s}")
                  ("\\subsubsection{%s}" . "\\subsubsection*{%s}"))
                 ("book-1+2+3"
                  "\\documentclass[11pt]{book}
[NO-DEFAULT-PACKAGES]
[PACKAGES]
[EXTRA]"
                  ("\\part{%s}" . "\\part*{%s}")
                  ("\\chapter{%s}" . "\\chapter*{%s}")
                  ("\\section{%s}" . "\\section*{%s}")
                  ("\\subsection{%s}" . "\\subsection*{%s}")
                  ("\\subsubsection{%s}" . "\\subsubsection*{%s}")))))))
#+end_src

*** [[info:org#In-buffer Settings][Buffer properties]]
:PROPERTIES:
:CUSTOM_ID: sec:buffer-properties
:END:

#+caption[Buffer properties]:
#+caption: Buffer properties.
#+name: lst:buffer-properties
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org
  (defun org-get-buffer-properties ()
    "Get all properties in buffer."
    (org-element-map (org-element-parse-buffer) 'keyword
      (lambda (el)
        (and ;; Use (upcase "property"), else it fails.
         (string= (org-element-property :key el) "PROPERTY")
         (let* ((strings (split-string (org-element-property :value el)))
                (value (string-join (cdr strings) " "))
                (name (car strings)))
           (cons name value)))))))
#+end_src

*** Org introspection
:PROPERTIES:
:CUSTOM_ID: sec:org-introspection
:END:

1. Listing [[lst:org-babel-active-languages]] produces a list containing language
   names that have ~org-babel-execute:LANGUAGE~ functions.
2. Listing [[lst:get-in-buffer-settings]] and [[lst:get-in-buffer-settings-result]] show
   how to access [[info:org#In-buffer Settings][In-buffer Settings (info)]].

#+caption[Find active Org Babel languages]:
#+caption: Find active Org Babel languages.
#+name: lst:org-babel-active-languages
#+header: :wrap "src emacs-lisp -n :eval never :tangle no"
#+begin_src emacs-lisp -n :exports both :results value pp :tangle no
(defun org-babel-active-languages ()
  (let (result)
    (mapatoms
     (lambda (x)
       (when (and
              (string-prefix-p "org-babel-execute:" (symbol-name x))
              ;; Get rid of all sub-modes in `ob-shell':
              (not (eq 'org-babel-shell-initialize (get x 'definition-name)))
              ;; Get rid of aliases:
              (not (eq 'symbol (type-of (symbol-function x)))))
         (when (symbol-file x)
           (push (string-remove-prefix "org-babel-execute:" (symbol-name x))
                 result)))))
    result))

(mapcar #'list (cl-sort (org-babel-active-languages) #'string-lessp))
#+end_src

#+caption[Active Org Babel languages]:
#+caption: Active Org Babel languages.
#+RESULTS: lst:org-babel-active-languages
#+begin_src emacs-lisp -n :eval never :tangle no
(("calc") ("emacs-lisp") ("eshell") ("fortran") ("latex") ("lisp")
 ("org") ("perl") ("python") ("ruby") ("shell"))
#+end_src

#+caption[Get "in-buffer" settings]:
#+caption: Get "in-buffer" settings.
#+name: lst:get-in-buffer-settings
#+header: :wrap "src emacs-lisp -n :eval never :tangle no"
#+begin_src emacs-lisp -n :exports both :results value pp :tangle no
(org-collect-keywords '("title" "author" "latex_class"))
#+end_src

#+caption[Get "in-buffer" settings result]:
#+caption: Get "in-buffer" settings result.
#+name: lst:get-in-buffer-settings-result
#+RESULTS: lst:get-in-buffer-settings
#+begin_src emacs-lisp -n :eval never :tangle no
(("TITLE" "Emacs setup for use with LaTeX, Lisp, Org, and Python")
 ("AUTHOR" "Gerard Vermeulen") ("LATEX_CLASS" "article"))
#+end_src

*** [[https://github.com/bdarcus/citar][Citar: citing bibliography]] with [[https://orgmode.org/][Org Mode]]
:PROPERTIES:
:CUSTOM_ID: sec:citing-bibliography
:END:

[[https://github.com/bdarcus/citar][Citar]] is a completing-read front-end to browse and act on BibTeX, BibLaTeX, as
well as CSL JSON bibliographic data with LaTeX, markdown, and org-cite editing
support.  In combination with vertico, embark, marginalia, and consult, [[https://github.com/bdarcus/citar][Citar]]
provides quick filtering and selecting of bibliographic entries from the
minibuffer as well as the option to run different commands on those
selections. The article [[https://kristofferbalintona.me/posts/202206141852/][Citations in org-mode: Org-cite and Citar]] tries to walk
you from understanding the general context (bibliography producer, text
processor, text to product converter) to an Emacs setup.  Listing
[[lst:set-oc+citar-options]] shows the =oc= and =citar= setup with binding of
{{{kbd(C-c b)}}} to src_emacs-lisp{(call-interactively 'org-cite-insert)} in
=org-mode-map=.

#+caption[Set =oc= and =citar= options]:
#+caption: Set =oc= and =citar= options.
#+name: lst:set-oc+citar-options
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'citar 'citar-embark)
  (with-eval-after-load 'embark
    (when (fboundp 'citar-embark-mode)
      (citar-embark-mode +1)))

  (with-eval-after-load 'oc
    (setopt org-cite-export-processors '((latex biblatex)
                                         (t csl))
            org-cite-global-bibliography '("~/VCS/research/refs.bib"))
    (if (not (require 'citar nil 'noerror))
        (user-error "Fails to require `citar' and to setup `citar' and `oc'")
      ;; Synchronize the two involved bibliographies.
      (setopt citar-bibliography org-cite-global-bibliography
              citar-library-file-extensions '("djvu" "pdf")
              ;; Here are the `.djvu' and `.pdf' files.
              citar-library-paths '("~/VCS/research/papers/"))
      (setopt org-cite-activate-processor 'citar
              org-cite-follow-processor 'citar
              org-cite-insert-processor 'citar)
      (with-eval-after-load 'org
        (keymap-set org-mode-map "C-c b" #'org-cite-insert)))))
#+end_src

Ref. [cite:@Schulte.MCSE.2011.41] shows that [[https://orgmode.org/][Org-mode]] is a simple, plain-text
markup language for hierarchical documents allowing intermingling of data, code,
and prose.  It serves as an example link to show how to use [[https://github.com/bdarcus/citar][Citar]] within this
setup, provided that =citar-bibliography= and =citar-library-paths= point to
valid directories and files.  In an [[https://orgmode.org/][Org-mode]] buffer this setup allows to:
1. Insert one or more [[https://orgmode.org/][Org-mode]] cite links:
   1. Type {{{kbd(C-c b)}}} or {{{kbd(M-x org-cite-insert)}}}.
   2. Choose one or multiple citations from the bibliography:
      1. by navigating to an item and selecting it with {{{kbd(RET)}}}
      2. by repeatingly navigating to an item and preselecting it with
         {{{kbd(TAB)}}}.  Select all preselected items with {{{kbd(RET)}}}.
2. View an electronic copy of an [[https://orgmode.org/][Org-mode]] cite link:
   1. Move point to the [[https://orgmode.org/][Org-mode]] cite link.
   2. Type {{{kbd(C-:)}}} or {{{kbd(M-x embark-dwim)}}}.
   3. Navigate to the corresponding library file.
   4. Select it.
3. Open the DOI of an [[https://orgmode.org/][Org-mode]] cite link:
   1. Move point to the [[https://orgmode.org/][Org-mode]] cite link.
   2. Type {{{kbd(C-:)}}} or {{{kbd(M-x embark-dwim)}}}.
   3. Navigate to the corresponding link.
   4. Select it.
4. The following =citar= functions may be useful too:
   1. src_emacs-lisp{(call-interactively 'citar-insert-citation)}.
   2. src_emacs-lisp[:results silent]{(call-interactively 'citar-open)}.

*** TODO Compare bibtex and biblatex
1. [[https://www.economics.utoronto.ca/osborne/latex/BIBTEX.HTM][Using bibtex: a short guide]]
2. [[https://www.tug.org/texlive//devsrc/Master/texmf-dist/doc/latex/biblatex/biblatex.pdf][The biblatex package]]
3. [[https://github.com/yuchenlin/rebiber][Rebiber: A tool for normalizing bibtex with official info]]
4. [[https://github.com/josephwright/biblatex-phys][A biblatex implementation of the AIP and APS bibliography style]]

#+caption[Delete =Biber= cache when =Biber= fails to make a bibliography]:
#+caption: Delete =Biber= cache when =Biber= fails to make a bibliography.
#+name: lst:delete-biber-cache
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  ;; https://tex.stackexchange.com/a/579356 answers
  ;; "How to solve Biber exiting with error code 2 but no error messages?"
  (defun biber-delete-cache ()
    "Delete the `Biber' cache to get rid of `Biber' exit code 2."
    (interactive)
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code "rm" "-rf" "$(biber --cache)")
      (if (= 0 exit-code)
          (message "%s" (string-trim output))
        (error "%s" (string-trim output))))))
#+end_src

*** [[https://github.com/tecosaur/engrave-faces#readme][Engrave Faces]]
:PROPERTIES:
:CUSTOM_ID: sec:engrave-faces
:END:

This package has a front-end that processes fontified buffers and pipes its
output into one of three back-ends for export to LaTeX, HTML and text with ANSI
escape codes.  It is an alternative to =minted= in case of LaTeX export or to
=htmlized= in case of HTML export.

The listings below work around one issue with spacing in the =pdf= output
resulting from use of the =engraved= source block back-end during =LaTeX=
export.  They increase the quality of the export results of this [[file:README.org][README.org]] and
the user-friendliness of this facility to a level acceptable for my workflow:
1. The default Org export configuration for engraving listings produces =pdf=
   output with a non-equidistant interline spacing in floating listings (those
   with captions) and equidistant interline spacing in non-floating =tcolorbox=
   environments (those without captions).  I have traced the non-equidistant
   interline spacing back to the =breakable= option of =Code= environments
   inside =listing= environments.  However, =tcolorbox= requires =breakable= for
   listings that do not fit on a page.  The filter
   =org-latex-engraved-source-block-filter= in listing
   [[lst:org-latex-engraved-source-block-filter]] and the
   =org-latex-engraved-preamble= customization in listing
   [[lst:smart-latex-engrave-org-source-blocks]] allow to engrave =org-mode= source
   blocks to "floating unbreakable with caption" or "non-floating breakable
   without caption" LaTeX environments.  This is a partial work-around, but part
   of my workflow.
2. Listing [[lst:ox-engraved-emacs-lisp-setup]] shows how to use this configuration.

#+caption[Engrave to floating unbreakable or non-floating breakable environments]:
#+caption: Define an =org-export= filter function to engrave =org-src-mode=
#+caption: blocks to floating unbreakable LaTeX environments or non-floating
#+caption: breakable LaTeX environments.
#+name: lst:org-latex-engraved-source-block-filter
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'engrave-faces)

(defun org-latex-engraved-source-block-filter (data _backend _info)
  "Replace \"Code\" with \"Breakable\" in non-floating DATA environments.

Set `org-latex-engraved-preamble' to define a Breakable (non-floating)
environment and an unbreakable Code (floating) environment."
  (unless (string-match "^\\\\DeclareTColorBox\\[\\]{Breakable}"
                        org-latex-engraved-preamble)
    (user-error
     "`org-latex-engraved-preamble' defines no `Breakable' environment"))
  (when (eq org-latex-src-block-backend 'engraved)
    ;; Transform only blocks matching at position 0.  Therefore, do
    ;; not transform blocks that are listing environments.
    (when (string-match "\\`\\\\begin{Code}\n" data)
      (setq data (replace-match "\\begin{Breakable}\n" t 'literal data))
      (if (string-match "^\\\\end{Code}\n" data)
          (setq data (replace-match "\\end{Breakable}\n" t 'literal data))
        (error "Match `^\\\\end{Code}' failure")))))
#+end_src

#+caption[Smart LaTeX engraving of =org-src-mode= blocks]:
#+caption: Smart LaTeX engraving of =org-src-mode= blocks.
#+name: lst:smart-latex-engrave-org-source-blocks
#+begin_src emacs-lisp -n :results silent
(defun smart-latex-engrave-org-source-blocks ()
  "Enable smart LaTeX engraving of `org-src-mode' blocks.

Sets backend and preamble locally to support floating unbreakable LaTeX
environments and non-floating breakable LaTeX environments by means of
`org-latex-engraved-source-block-filter'."
  (interactive)
  (when (require 'ox-latex nil 'noerror)
    (setq-local org-latex-src-block-backend 'engraved
                org-latex-engraved-preamble "\\usepackage{fvextra}
[FVEXTRA-SETUP]

% Make code and line numbers normalsize. Make line numbers grey.
\\renewcommand\\theFancyVerbLine{
  \\normalsize\\color{black!40!white}\\arabic{FancyVerbLine}}
% Do not rely on an eventual call to `engrave-faces-latex-gen-preamble'.
\\usepackage{xcolor}
\\providecolor{EfD}{HTML}{f7f7f7}
\\providecolor{EFD}{HTML}{28292e}
% To use \\DeclareTColorBox from the tcolorbox package:
\\usepackage[breakable,xparse]{tcolorbox}
% Define a Breakable environment to fontify code outside floats.
\\DeclareTColorBox[]{Breakable}{o}{
  colback=EfD, colframe=EFD, colupper=EFD,
  fontupper=\\normalsize\\setlength{\\fboxsep}{0pt},
  IfNoValueTF={#1}{
    boxsep=1pt, arc=1pt, outer arc=1pt, boxrule=0.5pt,
  }{
    boxsep=1pt, arc=0pt, outer arc=0pt, boxrule=0pt, leftrule=1pt
  },
  left=2pt, right=2pt, top=1pt, bottom=1pt, breakable
}
% Define an unbreakable Code environment to fontify code inside floats.
\\DeclareTColorBox[]{Code}{o}{
  colback=EfD, colframe=EFD, colupper=EFD,
  fontupper=\\normalsize\\setlength{\\fboxsep}{0pt},
  IfNoValueTF={#1}{
    boxsep=1pt, arc=1pt, outer arc=1pt, boxrule=0.5pt
  }{
    boxsep=1pt, arc=0pt, outer arc=0pt, boxrule=0pt, leftrule=1pt
  },
  left=2pt, right=2pt, top=1pt, bottom=1pt
}

[LISTINGS-SETUP]")))
#+end_src

#+caption[Emacs setup to use =engrave-faces-latex= in =org-mode= smartly]:
#+caption: Emacs setup to use =engrave-faces-latex= in =org-mode= smartly.
#+name: lst:ox-engraved-emacs-lisp-setup
#+begin_src emacs-lisp -n :exports code :results none :tangle no
(with-eval-after-load 'ox-latex
  (make-local-variable 'org-export-filter-src-block-functions)
  (add-to-list 'org-export-filter-src-block-functions
               'org-latex-engraved-source-block-filter)
  (when (fboundp 'smart-latex-engrave-org-source-blocks)
    (smart-latex-engrave-org-source-blocks)))
#+end_src

*** [[https://github.com/flexibeast/org-vcard#org-vcard---org-mode-support-for-vcard-export-and-import][Org-mode support for vCard import and export]]                   :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:org-vcard
:header-args:emacs-lisp: :tangle no
:END:

Import/export =vcf= files (Android phones) from/to Org-mode linear (level 1)
headline lists with the data in property drawers.

#+caption[Install =org-vcard= to read =vcf= files=]:
#+caption: Install =org-vcard= to read =vcf= files=.
#+name: lst:org-vcard
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'org-vcard)
#+end_src

*** [[info:org#Adding Hyperlink Types][Making Org hyperlink types (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:make-org-hyperlink-types
:END:

The listings below implement or reimplement three groups of =org-link= types:
1. Listing [[lst:org-ref-like-org-link-types]] defines =org-link= types for
   backwards compatibility with [[https://github.com/jkitchin/org-ref][org-ref]].
2. Listing [[lst:define-org-pdfview-link-type]] uses ideas from the definition of
   =docview-org-link= and =doi-org-link= types to define an =pdfview-org-link=
   type for use with [[https://github.com/vedang/pdf-tools][pdf-tools]].
3. Listing [[lst:patch-org-info-link-type]] patches the function =org-info-export=
   and listing [[lst:emacs-lisp-setup-buffer-local-ol-info]] sets the constants
   ~org-info-emacs-documents~ and ~org-info-other-documents~ as buffer local
   variables in order to export the =info-org-link= types in this document to
   =html= and LaTeX correctly.

#+caption[Define =org-link= types for backwards compatibility with =org-ref=]:
#+caption: Define =org-link= types for backwards compatibility with =org-ref=.
#+name: lst:org-ref-like-org-link-types
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ol
  (org-link-set-parameters "ac*" :export #'org-ref-ac*-export)
  (org-link-set-parameters "cite" :export #'org-ref-cite-export)
  (org-link-set-parameters "eqref" :export #'org-ref-eqref-export)
  (org-link-set-parameters "hyperlink" :export #'org-ref-hyperlink-export)
  (org-link-set-parameters "label" :export #'org-ref-label-export)
  (org-link-set-parameters "ref" :export #'org-ref-ref-export)

  (defun org-ref-ac*-export (path _desc backend _info)
    (pcase backend
      (`latex (format "\\gls*{%s}" path))
      (_ path)))

  (defun org-ref-cite-export (path _desc backend _info)
    (pcase backend
      (`latex (format "\\cite{%s}" path))
      (_ path)))

  (defun org-ref-eqref-export (path _desc backend _info)
    (pcase backend
      (`latex (format "\\eqref{%s}" path))
      (_ path)))

  (defun org-ref-hyperlink-export (path desc backend _info)
    (pcase backend
      (`latex (format "\\hyperlink{%s}{%s}" path desc))
      (_ path)))

  (defun org-ref-label-export (path _desc backend _info)
    (pcase backend
      (`latex (format "\\label{%s}" path))
      (_ path)))

  (defun org-ref-ref-export (path _desc backend _info)
    (pcase backend
      (`latex (format "\\ref{%s}" path))
      (_ path))))
#+end_src

#+caption[Define an =org-link= type for =pdf-tools=]:
#+caption: Define an =org-link= type for =pdf-tools=.
#+name: lst:define-org-pdfview-link-type
#+begin_src emacs-lisp -n :results silent
(declare-function pdf-view-current-page "pdf-macs" (&optional window))
(declare-function pdf-view-goto-page "pdf-view" (page &optional window))

(defun org-pdfview-export (link description backend _)
  "Export LINK as a \"pdfview\" type link using DESCRIPTION and export BACKEND.
The paths of the links export as file relative paths in order to
facilate moving single directories or whole directory trees."
  (let ((path (if (string-match "\\(.+\\)::.+" link)
                  (match-string 1 link)
                link))
        (desc (or description link)))
    (when (stringp path)
      (setq path (file-relative-name path))
      (pcase backend
        (`html (format "<a href=\"%s\">%s</a>" path desc))
        (`latex (format "\\href{%s}{%s}" path desc))
        (`ascii (format "%s (%s)" desc path))
        (_ path)))))

(defun org-pdfview-open (link _)
  "Open LINK as a \"pdfview\" type link."
  (string-match "\\(.*?\\)\\(?:::\\([0-9]+\\)\\)?$" link)
  (let ((path (match-string 1 link))
        (page (and (match-beginning 2)
                   (string-to-number (match-string 2 link)))))
    ;; Let Org mode open the file to respect org-link-frame-setup.
    (org-open-file path 1)
    (when page (pdf-view-goto-page page))))

(defun org-pdfview-store-link (&optional _interactive?)
  "Store a \"pdfview\" type link."
  (when (eq major-mode 'pdf-view-mode)
    (let* ((path buffer-file-name)
           (page (pdf-view-current-page))
           (text (concat "pdfview:" path "::" (number-to-string page))))
      (org-link-store-props
       :type "pdfview"
       :link text
       :description path))))

(with-eval-after-load 'ol
  (org-link-set-parameters "pdfview"
                           :follow #'org-pdfview-open
                           :export #'org-pdfview-export
                           :store #'org-pdfview-store-link))
#+end_src

#+caption[Patch =ol-info=]:
#+caption: Patch =ol-info=.
#+name: lst:patch-org-info-link-type
#+begin_src emacs-lisp -n :exports code :results silent
(declare-function org-info-map-html-url "ol-info" (filename))
(declare-function org-info--expand-node-name "ol-info" (node))

(with-eval-after-load 'ol-info
  (defun org-info-export (path desc format)
    "Export an info link.
See `org-link-parameters' for details about PATH, DESC and FORMAT."
    (let* ((parts (split-string path "#\\|::"))
           (manual (car parts))
           (node (or (nth 1 parts) "Top")))
      (pcase format
        (`html
         (format "<a href=\"%s#%s\">%s</a>"
                 (org-info-map-html-url manual)
                 (org-info--expand-node-name node)
                 (or desc path)))
        (`latex
         (format "\\href{%s\\#%s}{%s}"
                 (org-info-map-html-url manual)
                 (org-info--expand-node-name node)
                 (or desc path)))
        (`texinfo
         (let ((title (or desc "")))
           (format "@ref{%s,%s,,%s,}" node title manual)))
        (_ nil)))))
#+end_src

#+attr_latex: :options breaklines
#+caption[Patch buffer local =ol-info=]:
#+caption: Patch buffer local =ol-info=.
#+name: lst:emacs-lisp-setup-buffer-local-ol-info
#+begin_src emacs-lisp -n :exports code :results none :tangle no
(with-eval-after-load 'ol-info
  (make-variable-buffer-local 'org-info-emacs-documents)
  (setq org-info-emacs-documents (delete "org" org-info-emacs-documents))
  (make-variable-buffer-local 'org-info-other-documents)
  (setq org-info-other-documents
        (cl-union
         '(("consult" . "https://github.com/minad/consult")
           ("embark" . "https://github.com/oantolin/embark")
           ("magit" . "https://magit.vc/manual/magit.html")
           ("marginalia" . "https://github.com/minad/marginalia")
           ("org" . "https://orgmode.org/org.html")
           ("orderless" . "https://github.com/oantolin/orderless")
           ("sly" . "https://joaotavora.github.io/sly/")
           ("vertico" . "https://github.com/minad/vertico"))
         org-info-other-documents :test #'equal)))
#+end_src

*** [[https://bitspook.in/blog/extending-org-mode-to-handle-youtube-links/][Extending org-mode to handle YouTube links]]
:PROPERTIES:
:CUSTOM_ID: sec:make-org-yt-link-type
:END:

Listing [[lst:define-org-yt-link-type]] implements code to open the link to the
following YouTube video [[yt:eaZUZCzaIgw][Extending org-mode to handle YouTube links]] modifying
code from the following [[https://raw.githubusercontent.com/bitspook/spookmax.d/master/readme.org][Emacs setup]].

Opening [[yt:eaZUZCzaIgw][Extending org-mode to handle YouTube links]] may fail due to an old
(fixed) bug in =mpv=.  However, the link [[yt:48JlgiBpw_I][Absolute Beginner's Guide to Emacs]]
works always.

NOTE: Listing [[lst:define-org-yt-link-type][define org-yt-link type]] does only implement normal =html= links
instead of embedded video links, but listing [[lst:howto-embed-yt]] shows a working
=html= example of how to embed a YouTube video in an inline frame element.

#+caption[Define an =org-link= type for =YouTube=]:
#+caption: Define an =org-link= type for =YouTube=.
#+name: lst:define-org-yt-link-type
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'emms)
  ;; https://bitspook.in/blog/extending-org-mode-to-handle-youtube-paths/
  (defun org-yt-emms-open (path)
    "Open an \"YouTube\" PATH link with `emms' using \"mpv\"."
    (let ((link (format "https://www.youtube.com/watch?v=%s" path)))
      (require 'emms nil 'noerror)
      (emms-add-url link)
      (with-current-emms-playlist
        (save-excursion
          (emms-playlist-last)
          (emms-playlist-mode-play-current-track)))))

  (defun org-yt-url-browse-open (path)
    "Open an \"YouTube\" PATH link with `url-browse'."
    (let ((link (format "https://www.youtube.com/watch?v=%s" path)))
      (browse-url link)))

  (defun org-yt-export (path desc backend _)
    "Export an \"YouTube\" PATH link according to DESC and BACKEND."
    (pcase backend
      (`ascii
       (format "[%s] <https://www.youtube.com/watch?v=%s>" desc path))
      (`html
       (format "<a href=\"https://www.youtube.com/watch?v=%s\">%s</a>" path desc))
      (`latex
       (format "\\href{https://www.youtube.com/watch?v=%s}{%s}" path desc))
      (_ path)))

  (with-eval-after-load 'ol
    (org-link-set-parameters
     "yt" :follow #'org-yt-emms-open :export #'org-yt-export)))
#+end_src

#+caption[How to embed a =YouTube= video in =HTML=]:
#+caption: How to embed a =YouTube= video in =HTML=.
#+name: lst:howto-embed-yt
#+begin_src html -n :exports code :tangle yegge.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>ChatGPT: How to embed a YouTube video in HTML</title>
</head>
<body>
    <h1>Steve Yegge embedded YouTube video</h1>
    <iframe width="630" height="420"
            src="https://www.youtube.com/embed/lkIicfzPBys"
            allowfullscreen></iframe>
</body>
</html>
#+end_src

*** [[https://tecosaur.github.io/emacs-config/#translate-capital-keywords][Translate capital keywords (old) to lower case (new)]]
:PROPERTIES:
:CUSTOM_ID: sec:convert-upper-to-lower-case-keywords
:END:

#+caption[Convert upper to lower case keywords]:
#+caption: Convert upper to lower case keywords.
#+name: lst:convert-upper-to-lower-case-keywords
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  ;; https://tecosaur.github.io/emacs-config/#translate-capital-keywords
  (defun org-syntax-convert-keyword-case-to-lower ()
    "Convert all #+KEYWORDS to #+keywords."
    (interactive)
    (when (derived-mode-p 'org-mode)
      (save-excursion
        (goto-char (point-min))
        (let ((count 0)
              (case-fold-search nil))
          (while (re-search-forward "^[ \t]*#\\+[A-Z_]+" nil t)
            (unless (s-matches-p "RESULTS" (match-string 0))
              (replace-match (downcase (match-string 0)) t)
              (setq count (1+ count))))
          (message "Replaced %d keywords" count))))))
#+end_src

*** [[https://lists.gnu.org/archive/html/emacs-orgmode/2016-07/msg00394.html][Evaluate specific source blocks at load-time]]
:PROPERTIES:
:CUSTOM_ID: sec:load-time-specific-source-block-evaluation
:END:

[[https://emacs.stackexchange.com/questions/12938/how-can-i-evaluate-elisp-in-an-orgmode-file-when-it-is-opened][How to do load time source block evaluation]]

#+caption[Evaluate specific source blocks at load-time]:
#+caption: Evaluate specific source blocks at load-time.
#+name: lst:load-time-specific-source-block-evaluation
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (defun org-eval-named-blocks-with-infix (infix)
    "Evaluate all source blocks having INFIX in their name."
    (when (eq major-mode 'org-mode)
      (let ((blocks
             (org-element-map
                 (org-element-parse-buffer 'greater-element nil) 'src-block
               (lambda (block)
                 (when-let ((name (org-element-property :name block)))
                   (when (string-match-p infix name) block))))))
        (dolist (block blocks)
          (goto-char (org-element-property :begin block))
          (org-babel-execute-src-block)))))

  (defun org-eval-emacs-lisp-setup-blocks ()
    "Evaluate all source blocks having \"emacs-lisp-setup\" in their name."
    (interactive)
    (org-eval-named-blocks-with-infix "emacs-lisp-setup"))

  (defun org-eval-python-setup-blocks ()
    "Evaluate all source blocks having \"python-setup\" in their name."
    (interactive)
    (org-eval-named-blocks-with-infix "python-setup"))

  ;; Emacs looks for "Local variables:" after the last "newline-formfeed".
  (add-to-list 'safe-local-eval-forms '(org-eval-emacs-lisp-setup-blocks))
  (add-to-list 'safe-local-eval-forms '(org-eval-python-setup-blocks)))
#+end_src

*** [[info:org#Macro Replacement][Org-mode macro utilities]]
:PROPERTIES:
:CUSTOM_ID: sec:org-macro-utilities
:END:

Listing [[lst:by-backend-kbd-org-macro]] defines the Emacs Lisp utilities to
define the [[https://orgmode.org/][Org mode]] =kbd= macro in listing
[[lst:source-file-export-keyword-settings]].

#+attr_latex: :options breaklines
#+caption[Define Emacs Lisp utilities to define the =Org-mode= =kbd= macro]:
#+caption: Define Emacs Lisp utilities to define the =Org-mode= =kbd= macro.
#+name: lst:by-backend-kbd-org-macro
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (when (ensure-package-installation 'htmlize)
    (autoload 'htmlize-protect-string "htmlize" nil t))

  ;; https://orgmode.org/worg/org-contrib/babel/languages/ob-doc-LaTeX.html
  (defmacro by-backend (&rest body)
    "Help for org-export backend dependent execution."
    `(cl-case ',(bound-and-true-p org-export-current-backend) ,@body))

  (defun by-backend-kbd-org-macro (keys)
    "Help for an org-export backend dependent \"#+macro: kbd\"."
    (by-backend
     (ascii (format "`kbd(%s)'" keys))
     (html (format "@@html:<kbd>%s</kbd>@@" (htmlize-protect-string keys)))
     (latex (format "@@latex:\\colorbox{PowderBlue}{\\texttt{%s}}@@" keys)))))
#+end_src

*** Handle Python exceptions in ~ob-python~
:PROPERTIES:
:CUSTOM_ID: sec:handle-python-exceptions
:END:

Python exceptions are never visible while executing Python ~org-src-mode~
blocks.  Redirecting Python exceptions is a way to make them visible.  Listing
[[lst:redirect-python-exceptions]] redirects Python exceptions to the file
~stderr.arm~, listing [[lst:open-python-exceptions]] opens the file ~stderr.arm~ in
~auto-revert-mode~, and listing [[lst:demo-python-exceptions]] demonstrates the
redirection of Python exceptions to the file ~stderr.arm~.

#+caption[Redirect Python exceptions to a file]:
#+caption: Redirect Python exceptions to a file:
#+name: lst:redirect-python-exceptions
#+begin_src python -i -n :results silent :session :tangle no
import sys

file = open("stderr.arm", "w")
sys.stderr = file
#+end_src

#+caption[Open the redirected file in ~auto-revert-mode~]:
#+caption: Open the redirected file in ~auto-revert-mode~.
#+name: lst:open-python-exceptions
#+begin_src emacs-lisp -n :results silent :tangle no
(find-file "stderr.arm")
(auto-revert-mode)
#+end_src

#+caption[Demonstrate the redirection of Python exceptions to a file]:
#+caption: Demonstrate the redirectio of Python exceptions to a file.
#+name: lst:demo-python-exceptions
#+begin_src python -i -n :results silent :session :tangle no
variable
#+end_src

*** [[https://orgmode.org/worg/org-tests/index.html][Testing Org]]
:PROPERTIES:
:CUSTOM_ID: sec:testing-org
:END:

Listing [[lst:batch-org-testing]] shows the recommended way: use =make test= in a
clean Org git repository.  In addition, on my weird Darwin system, I do =ln -sf
VCS/org-mode/lisp= and =ln -sf VCS/org-mode/testing= to fix the command =make
repro=.

#+caption[Batch Org testing]:
#+caption: Batch Org testing: obligatory before mailing a patch.
#+name: lst:batch-org-testing
#+begin_src shell -n :eval never :tangle no
make test > out.txt 2>&1
#+end_src

*** LaTex preamble editing using [[info:org#Noweb Reference Syntax][Noweb (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:file-inclusion-and-noweb
:END:

Note: [[https://list.orgmode.org/87sfisf31o.fsf@posteo.net/][How to include LaTeX packages in a LaTeX export block]].

Listing [[lst:source-file-export-keyword-settings]] shows the preamble lines of this
[[file:README.org]] file.  It lists the export keyword settings, the definition of
the [[https://orgmode.org/][Org mode]] =kbd= macro and the source block that generates part of the LaTeX
preamble.  Listing [[lst:latex-header-1]], [[lst:latex-header-2]], [[lst:latex-header-3]],
[[lst:latex-header-4]], and [[lst:latex-header-5]] show the LaTeX source blocks that
contain the LaTeX preamble.  All LaTeX listings in this section *can be and are*
handled by [[info:org#Noweb Reference Syntax][noweb (info)]].

#+caption[Source file export keyword settings]:
#+caption: The preamble lines of README.org containing the export keyword
#+caption: settings, the definition of the Org-mode =kbd= macro, and the
#+caption: source block that generates part of the LaTeX preamble.
#+name: lst:source-file-export-keyword-settings
#+include: "README.org" src org -n :lines "1-17"

#+name: latex-header-1
#+begin_src latex -n :exports none
% Begin of the LaTeX preamble:
% See: https://list.orgmode.org/87o807r7fr.fsf@posteo.net/
% From: "Juan Manuel Macías" <maciaschain@posteo.net>
% To: orgmode <emacs-orgmode@gnu.org>
% Subject: [tip] Insert arbitrary LaTeX code at the beginning of any float environment
% Date: Sun, 08 May 2022 22:22:16 +0000
% Message-ID: <87o807r7fr.fsf@posteo.net>
% LuaLaTeX-, PdfLaTeX-, or XeTeX-COMPILER COMPATIBILITY:
% Prevent collisions by using font packages before compiler specific packages.
\usepackage{ifthen,ifluatex,ifxetex}
\ifthenelse{\boolean{luatex}}{
  \usepackage{fontspec}        % lualatex
}{\ifthenelse{\boolean{xetex}}{
    \usepackage{mathspec}        % xetex
  }{
    \usepackage[T1]{fontenc}     % pdflatex
    \usepackage[utf8]{inputenc}  % pdflatex
  }
}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{pifont}          % check mark (\ding{52}) and cross mark (\ding{56})
\usepackage{textcomp}        % \texttimes
\usepackage{wasysym}         % \diameter

% Org-mode REQUIREMENTS:
\usepackage{graphicx}
\usepackage{longtable}
\usepackage{wrapfig}
\usepackage{rotating}
\usepackage[normalem]{ulem}
\usepackage{capt-of}
\usepackage{hyperref}
% End of the 1st LaTeX header block.
#+end_src

#+caption[LaTeX preamble: replacing the =Org-mode= default packages]:
#+caption: LaTeX preamble: replacing the =Org-mode= default packages.
#+name: lst:latex-header-1
#+begin_src latex -n :exports code :noweb yes
<<latex-header-1>>
#+end_src

#+name: latex-header-2
#+begin_src latex -n :exports none
% LANGUAGE:
\usepackage{babel}
\usepackage{fvextra}
\usepackage{csquotes}

% LISTS:
\usepackage{enumitem}
\setlist{noitemsep}

% LISTINGS:
% Section 2.6 of caption-eng.pdf (texdoc caption) explains that the sign
% of "skip" depends on the assumption "position=above" or "position=below".
% The assumption should match the real caption position in the LaTeX code.
\usepackage{caption}
\usepackage[newfloat]{minted}
\captionsetup[listing]{position=below,skip=0em}
\usemintedstyle{xcode}

% TABLES:
% https://tex.stackexchange.com/questions/341205/
% what-is-the-difference-between-tabular-tabular-and-tabularx-environments
% https://emacs.stackexchange.com/questions/26179/
% change-org-mode-table-style-just-for-latex-export
% https://tex.stackexchange.com/questions/468585/
% table-formatting-using-siunitx
\usepackage{booktabs}
\usepackage{colortbl}
\usepackage{tabularx}  % DANGER: beware of Org table :width and :align options!
% End of the 2nd LaTeX header block.
#+end_src

#+caption[LaTeX preamble: language, lists and floats]:
#+caption: LaTeX preamble: language, lists and floats.
#+name: lst:latex-header-2
#+begin_src latex -n :exports code :noweb yes
<<latex-header-2>>
#+end_src

#+name: latex-header-3
#+begin_src latex -n :exports none
% PAGE LAYOUT:
\usepackage{fancyhdr}
\usepackage{lastpage}
\usepackage[
  headheight=20mm,
  top=40mm,
  bottom=20mm,
  left=0.1\paperwidth,
  right=0.1\paperwidth,
  heightrounded,
  verbose,
]{geometry}

% TECHNICS:
\usepackage{siunitx}
\usepackage{tikz}
% End of the 3rd LaTeX header block.
#+end_src

#+caption[LaTeX preamble: page layout and technics]:
#+caption: LaTeX preamble: page layout.
#+name: lst:latex-header-3
#+begin_src latex -n :exports code :noweb yes
<<latex-header-3>>
#+end_src

#+name: latex-header-4
#+begin_src latex -n :exports none
% FLOAT BARRIERS:
% https://tex.stackexchange.com/questions/118662/use-placeins-for-subsections
% Make section an implicit float barrier:
\usepackage[section]{placeins}
% Make subsection an implicit float barrier:
\makeatletter
\AtBeginDocument{%
  \expandafter\renewcommand\expandafter\subsection\expandafter{%
    \expandafter\@fb@secFB\subsection
  }%
}
\makeatother
% Make subsubsection an implicit float barrier:
\makeatletter
\AtBeginDocument{%
  \expandafter\renewcommand\expandafter\subsubsection\expandafter{%
    \expandafter\@fb@secFB\subsubsection
  }%
}
% End of the 4th LaTeX header block.
#+end_src

#+caption[LaTeX preamble: float barriers]:
#+caption: LaTeX preamble: float barriers.
#+name: lst:latex-header-4
#+begin_src latex -n :exports code :noweb yes
<<latex-header-4>>
#+end_src

#+name: latex-header-5
#+begin_src latex -n :exports none
% FANCY HEADERS AND FOOTERS:
% Add fancy headers and footers to normal pages.
\pagestyle{fancy}
\fancyhf{}
\renewcommand{\footrulewidth}{0.4pt}
\fancyfoot[C]{\emph{
    Emacs for \LaTeX{}, Lisp, Org, and Python -- Gerard Vermeulen
  }
}
\renewcommand{\headrulewidth}{0.4pt}
\fancyhead[L]{\includegraphics[height=1.8cm]{Org-mode-unicorn.png}}
\fancyhead[C]{
  Page: \thepage/\pageref{LastPage} \\
  \text{ } \\
  \text{ } \\
  DRAFT
}
\fancyhead[R]{\includegraphics[height=1.8cm]{Emacs-logo.png}}

% Add fancy header and footer to custom titlepage.
% https://tex.stackexchange.com/questions/506102/
% adding-header-and-footer-to-custom-titlepage
\fancypagestyle{titlepage}{%
  \fancyhf{}
  \renewcommand{\footrulewidth}{0.4pt}
  \fancyfoot[C]{\emph{
      Emacs for \LaTeX{}, Lisp, Org, and Python -- Gerard Vermeulen
    }
  }
  \renewcommand{\headrulewidth}{0.4pt}
  \fancyhead[L]{\includegraphics[height=1.8cm]{Org-mode-unicorn.png}}
  \fancyhead[C]{
    \pageref{LastPage} pages \\
    \text{ } \\
    \text{ } \\
    DRAFT
  }
  \fancyhead[R]{\includegraphics[height=1.8cm]{Emacs-logo.png}}
}
% End of the 5th and last LaTeX header block.
#+end_src

#+caption[LaTeX preamble: fancy headers and footers]:
#+caption: LaTeX preamble: fancy headers and footers.
#+name: lst:latex-header-5
#+begin_src latex -n :exports code :noweb yes
<<latex-header-5>>
#+end_src

*** [[info:org#LaTeX header and sectioning][Deprecated LaTeX preamble editing methods]]                      :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:easy-latex-preamble-editing
:END:

*NOTE:* This [[info:org#Top][Org (info)]] file uses the recommended method of noweb trickery in
Section [[#sec:file-inclusion-and-noweb]].

There are at least two deprecated (old and historic) ways to edit the Org
=#+latex_header:= and =#+latex_extra_header:= keywords easily
for export to LaTeX, see [[info:org#LaTeX header and sectioning][LaTeX header and sectioning (info)]].

The old way -- exploiting an idea of [[https://www.matem.unam.mx/~omar/][Omar Antolin Camarena]] -- is to code new
[[info:org#Editing Source Code][<LANGUAGE>-modes]] allowing to edit in LaTeX mode and to export to LaTeX code with
[[info:org#LaTeX specific export settings][correct LaTeX preamble export setting prefixes]].  Here, are links to three posts
exposing his idea:
1. [[https://www.reddit.com/r/orgmode/comments/7u2n0h/tip_for_defining_latex_macros_for_use_in_both/][Export LaTeX macros to LaTeX and HTML/MathJax preambles (reddit)]],
2. [[https://www.reddit.com/r/orgmode/comments/5bi6ku/tip_for_exporting_javascript_source_block_to/][Export JavaScript source blocks to script tags in HTML (reddit)]],
3. [[https://emacs.stackexchange.com/questions/28301/export-javascript-source-block-to-script-tag-in-html-when-exporting-org-file-to][Export JavaScript source blocks to script tags in HTML (SX)]].
Listing [[lst:org-babel-latex-header-blocks]] implements this way by means of two
new [[info:org#Editing Source Code][<LANGUAGE>-modes]]: =latex-header= and =latex-extra-header=.

The old way is to define two Org Babel languages (=latex-extra-header= and
=latex-header=) as done in Listing [[lst:org-babel-latex-header-blocks]]. The
historic way is to use a special export attribute as in the function
=org-latex-header-blocks-filter= in [[https://git.sr.ht/~bzg/org-contrib/tree/master/item/lisp/ox-extra.el][ox-extra.el]].  Apparently, nobody is using
this broken function (broken, since it relies on support only in org-mode before
=2014-11-11=).  Listing [[lst:org-latex-header-blocks-filter]] proposes a fix for
=org-latex-header-blocks-filter=.  This setup keeps the deprecated ways for
backwards compatibility.  A practical difference is that new way source blocks
(contrary to old way export blocks) do not work in [[info:org#Export Settings][#+SETUPFILE: <FILE>]], but only
in [[info:org#Export Settings][#+INCLUDE: <FILE>]] files.

#+caption[New =<LANGUAGE>-modes= to edit the LaTeX preamble easily]:
#+caption: Add =latex-header= and =latex-extra-header=  language modes to edit
#+caption: LaTeX preamble =latex_header= and =latex_extra_header= export options
#+caption: easily.
#+name: lst:org-babel-latex-header-blocks
#+begin_src emacs-lisp -n :exports code :results silent :tangle no
(with-eval-after-load 'emacs
  (defun prefix-all-lines (prefix body)
    (with-temp-buffer
      (insert body)
      (string-insert-rectangle (point-min) (point-max) prefix)
      (buffer-string)))

  (defun org-babel-execute:latex-extra-header (body _params)
    "Execute a block of LaTeX extra header lines with org-babel.
Calling `org-babel-execute-src-block' calls this function and
prefixes all lines with \"#+latex_extra_header: \"."
    (prefix-all-lines "#+latex_extra_header: " body))

  (defun org-babel-execute:latex-header (body _params)
    "Execute a block of LaTeX header lines with org-babel.
Calling `org-babel-execute-src-block' calls this function and
prefixes all lines with \"#+latex_header: \"."
    (prefix-all-lines "#+latex_header: " body))

  (defvar org-babel-default-header-args:latex-extra-header
    '((:exports . "results") (:results . "raw")))

  (defvar org-babel-default-header-args:latex-header
    '((:exports . "results") (:results . "raw")))

  (with-eval-after-load 'org-src
    (add-to-list 'org-src-lang-modes '("latex-header" . latex))
    (add-to-list 'org-src-lang-modes '("latex-extra-header" . latex))))
#+end_src

#+caption[Convert marked LaTeX export blocks to LaTeX header lines]:
#+caption: Convert marked LaTeX export blocks to LaTeX header lines.
#+name: lst:org-latex-header-blocks-filter
#+begin_src emacs-lisp -n :results silent :tangle no
(with-eval-after-load 'ox
  (defun org-latex-header-blocks-filter (backend)
    "Convert marked LaTeX export blocks to \"#+latex_header: \" lines.
The marker is a line \"#+header: :header yes\" preceding the block.

For instance, the LaTeX export block

,#+header: :header yes
,#+begin_export latex
% This line converts to a LaTeX header line.
,#+end_export

converts to

\"#+latex_header: % This line converts to a LaTeX header line.\"."
    (when (org-export-derived-backend-p backend 'latex)
      (let ((blocks
             (org-element-map
                 (org-element-parse-buffer 'greater-element nil) 'export-block
               (lambda (block)
                 (let ((type (org-element-property :type block))
                       (header (org-export-read-attribute :header block :header)))
                   (when (and (string= type "LATEX") (string= header "yes"))
                     block))))))
        (mapc (lambda (block)
                ;; Set point to where to insert LaTeX header lines
                ;; after deleting the block.
                (goto-char (org-element-property :post-affiliated block))
                (let ((lines
                       (split-string (org-element-property :value block) "\n")))
                  (delete-region (org-element-property :begin block)
                                 (org-element-property :end block))
                  (dolist (line lines)
                    (insert (concat "#+latex_header: "
                                    (replace-regexp-in-string "\\` *" "" line)
                                    "\n")))))
              ;; Reverse to go upwards to avoid wrecking the list of
              ;; block positions in the file that would occur in case
              ;; of going downwards.
              (reverse blocks)))))

  ;; Push the filter on the hook.
  (cl-pushnew #'org-latex-header-blocks-filter
              org-export-before-parsing-functions))
#+end_src

*** [[info:org#HTML Export][HTML export (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:html-export
:END:

The code label and link feature in [[info:Org#Literal Examples][Literal Examples (info)]] does not integrate
with LaTeX export.

#+caption[Set HTML export options]:
#+caption: Set HTML export options.
#+name: lst:set-html-export-options
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ox-html
  ;; (Info-find-node "Org" "Literal Examples")
  (setopt org-html-head-include-scripts t)
  ;; Force `org-index-capture' loading after lazy `ox-html' loading.
  (require 'org-index-capture nil 'noerror))
#+end_src

*** [[info:org#LaTeX specific export settings][Advanced LaTeX export settings]]
:PROPERTIES:
:CUSTOM_ID: sec:advanced-latex-export-settings
:END:

Listing [[lst:ox-latex-emacs-lisp-setup]] initializes the buffer local variables
=org-latex-classes=, =org-latex-title-command=, =org-latex-toc-command=, and
=org-latex-subtitle-format=.  Read the documentation strings to understand how
those variables control exporting from Org-mode to LaTeX.

#+caption[Define buffer local =ox-latex= variables]:
#+caption: Define buffer local =ox-latex= variables.
#+name: lst:ox-latex-emacs-lisp-setup
#+begin_src emacs-lisp -n :exports code :results none :tangle no
(when (require 'ox-latex nil 'noerror)
  ;; https://emacs.stackexchange.com/questions/47347/
  ;; customizing-org-latex-title-command-to-edit-title-page
  ;; https://tex.stackexchange.com/questions/506102/
  ;; adding-header-and-footer-to-custom-titlepage
  (make-local-variable 'org-latex-classes)
  (cl-pushnew '("article-local"
                "\\documentclass[11pt]{article}
[NO-DEFAULT-PACKAGES]
[PACKAGES]
[EXTRA]"
                ("\\section{%s}" . "\\section*{%s}")
                ("\\subsection{%s}" . "\\subsection*{%s}")
                ("\\subsubsection{%s}" . "\\subsubsection*{%s}")
                ("\\paragraph{%s}" . "\\paragraph*{%s}")
                ("\\subparagraph{%s}" . "\\subparagraph*{%s}"))
              org-latex-classes :key #'car :test #'equal)

  (setq-local org-latex-title-command "\\begin{titlepage}
  %% https://emacs.stackexchange.com/questions/47347/
  %% customizing-org-latex-title-command-to-edit-title-page
  %% https://tex.stackexchange.com/questions/506102/
  %% adding-header-and-footer-to-custom-titlepage
  \\thispagestyle{titlepage}
  \\begin{center}
    %% Title
    \\begin{Huge}
      {\\bf %t} \\\\
      \\vspace{1em}
    \\end{Huge}
    %% Author
    \\begin{Large}
      {\\bf %a} \\\\
      \\vspace{1em}
    \\end{Large}
  \\end{center}
\\end{titlepage}")
  (setq-local org-latex-toc-command "
\\tableofcontents\\label{toc}
\\listoflistings
\\listoftables
\\newpage
")
  (setq-local org-latex-subtitle-format ""))
#+end_src

*** [[https://orgmode.org/worg/dev/org-syntax-edited.html][Org Syntax]]
:PROPERTIES:
:CUSTOM_ID: sec:org-syntax
:END:

Two tools to grok how [[https://orgmode.org/worg/dev/org-element-api.html][Org mode parsing]] works are the [[https://orgmode.org/worg/dev/org-syntax-edited.html][Org Syntax]] specification
and the [[http://xahlee.info/emacs/emacs/elisp_parse_org_mode.html][Org mode parser tutorial]]. The [[https://orgmode.org/worg/dev/org-element-api.html][Org element parsing API]] boils down to three
functions:
1. The function [[https://orgmode.org/worg/dev/org-element-api.html#global][~org-element-parse-buffer~]] implements a fully recursive buffer
   parser that returns an abstract syntax tree.
2. The functions [[https://orgmode.org/worg/dev/org-element-api.html#local][~org-element-at-point~ and ~org-element-context~]] return
   information on the document structure around point either at the element
   level or at the object level in case of ~org-element-context~.
Listing [[lst:grok-org-element-tree]] improves the [[http://xahlee.info/emacs/emacs/elisp_parse_org_mode.html][Org mode parser tutorial]] by
defining interactive wrappers that pretty print the results of those
non-interactive =org-element= functions to an =Emacs-lisp= buffer.

#+caption[Grok how =org-element= parses your document]:
#+caption: Grok how =org-element= parses your document.
#+name: lst:grok-org-element-tree
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'org-element
  (defconst grok-org-output
    "*Grok Org Element Output*"
    "Grok Org output buffer name.")

  (defun grok-org-element-at-point ()
    "Call `org-element-at-point' interactively and pretty-print."
    (interactive)
    (pp-display-expression
     (org-element-at-point) grok-org-output))

  (defun grok-org-element-context ()
    "Call `org-element-context' interactively and pretty-print."
    (interactive)
    (pp-display-expression
     (org-element-context) grok-org-output))

  (defun grok-org-element-parse-buffer ()
    "Call `org-element-parse-buffer' interactively and pretty-print."
    (interactive)
    (let ((what (completing-read
                 "granularity: "
                 '(headline element greater-element object)
                 nil 'require-match)))
      (pp-display-expression
       (org-element-parse-buffer what) grok-org-output)))

  (defun grok-org-element-parse-whole-buffer ()
    "Like `grok-org-element-parse-buffer' from point 1 and sans granularity."
    (interactive)
    (org-with-point-at 1
      (pp-display-expression (org-element-parse-buffer) grok-org-output)))

  (defun grok-org-heading-components ()
    "Call `org-heading-components' interactively and pretty-print."
    (interactive)
    (pp-display-expression
     (org-heading-components) grok-org-output))

  (defun grok-org-element-lineage ()
    "Call `org-element-lineage' interactively and pretty-print."
    (interactive)
    (org-load-modules-maybe)
    (pp-display-expression
     (org-element-lineage (org-element-context) nil t) grok-org-output)))
#+end_src

** Grammar, spelling, and style tools
:PROPERTIES:
:CUSTOM_ID: sec:writing-tools
:END:

*** [[info:emacs#Abbrevs][Abbrevs (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:writing-abbreviations
:END:

[[https://www.masteringemacs.org/][Mickey Peterson]] has posted [[https://www.masteringemacs.org/article/correcting-typos-misspellings-abbrev][Correcting Typos and Misspellings with Abbrev]] showing
how to use [[info:emacs#Keyboard Macros][Keyboard Macros (info)]] to exploit [[https://en.wikipedia.org/wiki/Wikipedia:Lists_of_common_misspellings/For_machines][Wikipedia's list of common
misspellings for machines]].  Listing [[lst:misspellings-abbrev]] defines his keyboard
macro under the name =misspellings-abrev=.  I have used those directions to
define src_emacs-lisp[:results silent]{(describe-variable 'global-abbrev-table)}
and to store it in src_emacs-lisp[:results none]{(describe-variable
'abbrev-file-name)} to manage its changes with git.  I can change the
abbreviation definitions in this file by means of:
1. Execute src_emacs-lisp[:results silent]{(edit-abbrevs)} to alter abbreviation
   definitions by editing an =*Abbrevs*= buffer.
2. Add, edit, or remove definitions of the form ="source" 1 "target"= under the
   global or a mode-specific table.
3. Execute src_emacs-lisp{(abbrev-edit-save-buffer)} to save all user
   abbreviation definitions in the current buffer.

#+caption[Definition of the =misspellings-abbrev= keyboard macro]:
#+caption: Definition of the =misspellings-abbrev= keyboard macro.
#+name: lst:misspellings-abbrev
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (defun browse-common-misspellings ()
    "Open the Wikipedia page of common misspellings for machines in EWW."
    (interactive)
    (eww (concat "https://en.wikipedia.org/wiki/Wikipedia"
                 ":Lists_of_common_misspellings/For_machines")))

  (fset 'misspellings-abbrev
        (kmacro-lambda-form
         [?\C-s ?- ?> return backspace backspace ?\C-k ?\C-x ?a ?i ?g ?\C-y return]
         0 "%d"))

  (setq-default abbrev-mode t))
#+end_src

*** TODO [[https://dict.org/bin/Dict][DICT.org]] local server fails on Darwin
:PROPERTIES:
:CUSTOM_ID: sec:writing-dict
:END:

Evaluating src_emacs-lisp{(dictionary)} connects to a local or remote =dictd=
server.  The following links explain how to configure and use =dictd=:
1. [[https://jpmens.net/2020/03/08/looking-up-words-with-dict/][Looking up words with DICT]]
2. [[https://www.rfc-editor.org/rfc/rfc2229.html][RFC 2229: A Dictionary Server Protocol]]
3. [[https://www.masteringemacs.org/article/wordsmithing-in-emacs][Wordsmithing in Emacs]]

I am using the following Debian Bullseye dictionaries on Darwin and Gentoo:
1. [[http://ftp.fr.debian.org/debian/pool/main/d/dict-devil/dict-devil_1.0-13.1_all.deb][dict-devil_1.0-13.1_all.deb]]
2. [[http://ftp.fr.debian.org/debian/pool/main/d/dict-foldoc/dict-foldoc_20201018-1_all.deb][dict-foldoc_20201018-1_all.deb]]
3. [[http://ftp.fr.debian.org/debian/pool/main/d/dict-gcide/dict-gcide_0.48.5+nmu1_all.deb][dict-gcide_0.48.5+nmu1_all.deb]]
4. [[http://ftp.fr.debian.org/debian/pool/main/d/dict-jargon/dict-jargon_4.4.7-3.1_all.deb][dict-jargon_4.4.7-3.1_all.deb]]
5. [[http://ftp.fr.debian.org/debian/pool/main/v/vera/dict-vera_1.24-1_all.deb][dict-vera_1.24-1_all.deb]]
6. [[http://ftp.fr.debian.org/debian/pool/main/w/wordnet/dict-wn_3.0-36_all.deb][dict-wn_3.0-36_all.deb]]

#+caption[Resource file for =dict= on =Darwin=]:
#+caption: Resource file for =dict= on =Darwin=.
#+name: lst:darwin-dict-resource-file
#+header: :tangle (if (eq 'darwin system-type) "~/.dictrc" "no")
#+begin_src conf -n
# https://jpmens.net/2020/03/08/looking-up-words-with-dict/
server 127.0.0.1 {
   port 2628
}
# Local Variables:
# mode: conf-unix
# End:
#+end_src

#+caption[Make a configuration file for =dictd= on =Darwin=]:
#+caption: Make a configuration file for =dictd= on =Darwin=.
#+name: lst:dictd-configuration-file
#+begin_src shell -n :eval (if (eq 'darwin system-type) "yes" "never") :results silent
cat > ~/.dictd.conf <<EOF
# https://www.masteringemacs.org/article/wordsmithing-in-emacs
database devil {
   data "${HOME}/.local/share/dictd/devil.dict.dz"
   index "${HOME}/.local/share/dictd/devil.index"
}
database foldoc {
   data "${HOME}/.local/share/dictd/foldoc.dict.dz"
   index "${HOME}/.local/share/dictd/foldoc.index"
}
database gcide {
   data "${HOME}/.local/share/dictd/gcide.dict.dz"
   index "${HOME}/.local/share/dictd/gcide.index"
}
database jargon {
   data "${HOME}/.local/share/dictd/jargon.dict.dz"
   index "${HOME}/.local/share/dictd/jargon.index"
}
database vera {
   data "${HOME}/.local/share/dictd/vera.dict.dz"
   index "${HOME}/.local/share/dictd/vera.index"
}
database wn {
   data "${HOME}/.local/share/dictd/wn.dict.dz"
   index "${HOME}/.local/share/dictd/wn.index"
}
EOF
#+end_src

#+caption[Run =dictd= in debug mode on =Darwin=]:
#+caption: Run =dictd= in debug mode on =Darwin=.
#+name: lst:darwin-dictd-launch
#+begin_src shell -n :eval never :tangle no
# https://jpmens.net/2020/03/08/looking-up-words-with-dict/
/usr/local/sbin/dictd \
    --config .dictd.conf \
    --verbose \
    --logfile .dictd.log \
    -d nodetach
#+end_src

*** [[https://github.com/bnbeckwith/writegood-mode#readme][Writegood mode]]
:PROPERTIES:
:CUSTOM_ID: sec:writing-writegood-mode
:END:

[[https://github.com/bnbeckwith/writegood-mode#readme][Writegood mode]] is a minor mode to aid in finding common writing problems.  The
post [[http://matt.might.net/articles/shell-scripts-for-passive-voice-weasel-words-duplicates/][Matt Might's "My Ph.D. advisor rewrote himself in bash" scripts]] inspired
this mode.  Listing [[lst:configure-writegood-mode]] configures [[https://github.com/bnbeckwith/writegood-mode#readme][writegood mode]] and
enables =writegood-mode= for =text-mode= buffers.  Therefore, the best way use
it for this buffer is by typing {{{kbd(C-c C-e t U)}}} to export the it to a
=text-mode= buffer where the =writegood-mode= faces are more visible.

#+caption[Configure =writegood-mode=]:
#+caption: Configure =writegood-mode=.
#+name: lst:configure-writegood-mode
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'writegood-mode)
  (add-hook 'after-init-hook
            (defun on-after-change-mode-hook-enable-writegood-mode ()
              (add-hook 'after-change-major-mode-hook
                        (defun enable-writegood-mode ()
                          (when (derived-mode-p '(org-mode text-mode))
                            (writegood-mode +1)))))
            'depth)

  (global-set-key (kbd "C-c g") #'writegood-mode))
#+end_src

** [[info:emacs#Which Function][Which-function-mode (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:which-function-mode
:END:

Listing [[lst:setup-which-function-mode]] sets ~which-function-mode~ options.  The
post [[https://codelearn.me/2024/02/02/emacs-which-function-mode.html][Emacs: which-function-mode]] claims that ~which-function-mode~ works in
~org-mode~.  This is true in case all document headlines are simple, but is not
true in case document headlines contain links.  The code in listing
[[lst:define-for-which-func-functions]] has stolen ideas from the following links:
- [[https://list.orgmode.org/20240205.141235.268481480563517065.teika@gmx.com/][Show current org-mode headline in frame header]].
- [[https://emacs.stackexchange.com/questions/30894/][Show current org-mode headline in modeline]].

#+caption[Setup ~which-function-mode~]:
#+caption: Setup ~which-function-mode~.
#+name: lst:setup-which-function-mode
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'which-func
  (setopt which-func-modes '(emacs-lisp-mode org-mode pdf-view-mode)))
#+end_src

#+caption[Define functions for ~which-func-functions~]:
#+caption: Define functions for ~which-func-functions~.
#+name: lst:define-for-which-func-functions
#+begin_src emacs-lisp -n :results silent
;; https://emacs.stackexchange.com/questions/30894/
(declare-function pdf-info-outline "pdf-info" (&optional file-or-buffer))
(declare-function org-element-type-p "org-element-ast" (node types))
(defvar which-func-functions nil)

(defun which-func-org-function ()
  "Return level and title of the current headline.
Return the document title when point is above the first headline."
  (interactive) ;; Keep this function interactive for fixing.
  (when (eq major-mode 'org-mode)
    (let (text)
      ;; Handle point eventually above the first headline.
      (unless (org-at-heading-p)
        (save-excursion
          (org-previous-visible-heading 1)
          (let ((eap (org-element-at-point)))
            (when (org-element-type-p eap 'keyword)
              (setq text (format "0|%s" (org-element-property :value eap)))))))
      ;; Handle point anywhere else.
      (unless text
        (let* ((chain (org-get-outline-path t))
               (count (length chain)))
          (setq text (format "%s|%s" count (nth (1- count) chain)))))
      text)))
(add-to-list 'which-func-functions 'which-func-org-function)

(defun which-func-pdf-view-function ()
  "Return the title of the current headline.
Return \"Front Matter\" when current page is above the first headline."
  (interactive) ;; Keep this function interactive for fixing.
  (when (eq major-mode 'pdf-view-mode)
    (let* ((current-page (pdf-view-current-page))
           (outline (pdf-info-outline (current-buffer)))
           (hl-count (length outline))
           (hl-index 0)
           (hl-page 0)
           (old-title "Front Matter")
           (new-title old-title))
      ;; Return the first headline on a page which is better than nothing.
      ;; I can't do better, since `pdf-view-mode' has no notion of point.
      (while (and (< hl-index hl-count) (< hl-page current-page))
        (setq old-title new-title)
        (setq hl-page (alist-get 'page (nth hl-index outline)))
        (setq new-title (alist-get 'title (nth hl-index outline)))
        (cl-incf hl-index))
      (if (< current-page hl-page) old-title new-title))))
(add-to-list 'which-func-functions 'which-func-pdf-view-function)
#+end_src

* [[info:emacs#Saving Emacs Sessions][Saving Emacs sessions (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:desktop
:END:

Listing [[lst:desktop-setup][setup desktop]] makes Emacs save its state between closing its session to
opening the next session.

#+caption[Setup =desktop= to save Emacs sessions]:
#+caption: Setup =desktop= to save Emacs sessions.
#+name: lst:desktop-setup
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  ;; GAV: I fail to implement the idea of ChatGPT on how to reload
  ;; `eww' pages automatically while restoring the desktop (idea is to
  ;; add save and restore handlers to `desktop-buffer-mode-handlers').
  ;; GAV: (setopt eww-restore-desktop t) fails and starts hesitantly.
  ;; GAV: I fail to code a function for setting the
  ;; `desktop-buffers-not-to-save-function' option.
  (setopt desktop-buffers-not-to-save
          (rx bos (or "*Apropos" "compilation*"))
          desktop-modes-not-to-save
          '(emacs-lisp-mode image-mode tags-table-mode))

  (desktop-save-mode t))
#+end_src

* Programming Tools
:PROPERTIES:
:CUSTOM_ID: sec:programming-tools
:END:

** [[info:eglot#Top][Eglot (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:eglot
:END:

[[https://github.com/joaotavora/eglot#readme][Emacs polyGLOT (Eglot)]] is an Emacs language-server-protocol client that stays
out of your way.  [[info:eglot#Top][Eglot (info)]] is a builtin since Emacs-29.1.  The following
listings contribute to a programming language mode independent [[https://github.com/joaotavora/eglot][Eglot]]
configuration:
1. Listing [[lst:minimal-eglot-setup][minimal Eglot setup]] adds key bindings to =eglot-mode-keymap=.
2. Listing [[lst:setup-oglot]] uses [[https://github.com/gav451/oglot#][oglot]] to enable using [[https://github.com/joaotavora/eglot][Eglot]] in =org-src-mode=
   Python buffers (and not for Julia buffers).
3. Listing [[lst:eglot-maybe-ensure]] starts [[https://github.com/joaotavora/eglot][Eglot]] in case of proper programming
   modes and proper directory local variables (meaning in presence of a proper
   file [[info:emacs#Directory Variables][.dir-locals.el]] in the root directory of any project using proper
   programming modes).
4. Listing [[lst:whiten-black]] defines Emacs Lisp functions to undo (whiten) some
   output of [[https://black.readthedocs.io/en/stable/][Black]] after src_emacs-lisp[:results silent]{(org-babel-tangle)}.

#+caption[Ensure =eglot= installation with minimal setup]:
#+caption: Ensure =eglot= installation with minimal setup.
#+name: lst:minimal-eglot-setup
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'eglot
  (keymap-set eglot-mode-map "C-c n" 'flymake-goto-next-error)
  (keymap-set eglot-mode-map "C-c p" 'flymake-goto-prev-error)
  (keymap-set eglot-mode-map "C-c r" 'eglot-rename))
#+end_src

#+caption: Setup ~oglot~ for ~python-mode~.
#+name: lst:setup-oglot
#+begin_src emacs-lisp -n :results silent
(when (and (package-installed-p 'oglot)
           (require 'oglot nil 'noerror))
  (setopt oglot-maybe-ensure-modes '(python-mode)))
#+end_src

#+caption[Start =eglot= in case of a proper =dir-local-variables-alist=]:
#+caption: Start =eglot= in case of a proper =dir-local-variables-alist=.
#+name: lst:eglot-maybe-ensure
#+begin_src emacs-lisp -n :results silent
(defun eglot-maybe-ensure ()
  "Call `eglot-ensure' under favorable conditions."
  (when (and (apply #'derived-mode-p '(python-mode))
             (assoc 'eglot-workspace-configuration dir-local-variables-alist))
    (eglot-ensure)))

;; The two hooks `after-change-major-mode-hook' and
;; `hack-local-variables-hook' are OK, but language mode hooks like
;; `python-mode-hook' are not.
(add-hook 'after-change-major-mode-hook #'eglot-maybe-ensure)
#+end_src

#+caption[Whiten Black]:
#+caption: Whiten Black
#+name: lst:whiten-black
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (defun black-python-sequence ()
    "Try to find a Blackened Python sequence to whiten."
    (interactive)
    (if (derived-mode-p 'python-mode)
        (re-search-forward "[[(][ \t]*$" nil t)
      (org-narrow-to-block)
      (re-search-forward "[[(][ \t]*$" nil t)
      (widen)))

  (defun whiten--python-sequence ()
    "Whiten a Blackened Python sequence without narrowing.
Call `widen' after an `user-error'."
    (if (not (and (looking-at-p "[ \t]*$")))
        (user-error "Call `widen': not seeing `new-line'")
      (skip-chars-backward " \t\\[\\(")
      (if (not (looking-at-p "[ \t]*[[(][ \t]*$"))
          (user-error "Call `widen': not seeing `[' or `(' before `new-line'")
        (fixup-whitespace)
        (skip-chars-forward " \\[\\(")
        (kill-line)
        (fixup-whitespace)
        (move-end-of-line 1)
        (while (and (eq ?\, (char-before)))
          (kill-line)
          (fixup-whitespace)
          (move-end-of-line 1))
        (save-excursion
          (when (memq (char-before) '(?\) ?\]))
            (goto-char (1- (point)))
            (delete-char -1))))))

  (defun whiten-python-sequence ()
    "Whiten a Blackened Python sequence.  Call `widen' after an `user-error'."
    (interactive)
    (if (derived-mode-p 'python-mode)
        (whiten--python-sequences)
      (org-narrow-to-block)
      (whiten--python-sequence)
      (widen))))
#+end_src

** [[https://github.com/lassik/emacs-format-all-the-code#readme][Format-all]]
:PROPERTIES:
:CUSTOM_ID: sec:format-all
:END:

Listing [[lst:configure-format-all]]:
1. Configures [[https://github.com/lassik/emacs-format-all-the-code#readme][format-all]] which is a package that provides an universal interface
   to code formatters of more than 60 computer languages.
2. Adds =format-all-org-babel-post-tangle= to =org-babel-post-tangle-hook= to
   format tangled Python code.

#+caption[Configure =format-all=]:
#+caption: Configure =format-all=.
#+name: lst:configure-format-all
#+begin_src emacs-lisp -n :results silent
;; https://github.com/lassik/emacs-format-all-the-code#readme
;; https://ianyepan.github.io/posts/format-all/
;; https://jamesaimonetti.com/posts/formatting-tangled-output-in-org-mode/
(when (ensure-package-installation 'format-all)
  ;; `format-all' defines `format-all-buffer' as an autoloaded command.
  (with-eval-after-load 'ob-tangle
    (add-hook
     'org-babel-post-tangle-hook
     (defun format-all-org-babel-post-tangle ()
       (when (derived-mode-p 'python-mode)
         (setq-local format-all-formatters '(("Python" black)))
         (format-all-buffer)
         (save-buffer)
         (message "Saved reformatted tangled buffer `%s'"
                  (buffer-file-name)))))))
#+end_src

** [[info:flymake#Top][Flymake (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:flymake
:END:

Flymake is an universal on-the-fly syntax checker for Emacs. It is a requirement
of [[https://github.com/joaotavora/eglot][eglot]], but you can use it without [[https://github.com/joaotavora/eglot][eglot]] for instance in [[https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/progmodes/python.el][python-mode]] buffers
that do not visit a file.  Listing [[lst:configure-flymake]] aliases =list-errors=
(new) to =flymake-show-buffer-diagnostics= (old).

#+caption[Configure =Flymake=]:
#+caption: Configure =Flymake=
#+name: lst:configure-flymake
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'flymake
  (defalias 'list-errors #'flymake-show-buffer-diagnostics
    "Show a list of Flymake diagnostics for current buffer.")

  (keymap-set flymake-mode-map "M-n" 'flymake-goto-next-error)
  (keymap-set flymake-mode-map "M-p" 'flymake-goto-prev-error))
#+end_src

* Programming Modes
:PROPERTIES:
:CUSTOM_ID: sec:programming-languages
:END:

** [[https://dept-info.labri.fr/~strandh/Teaching/PFS/Common/Strandh-Tutorial/Dir-symbolic.html][Common Lisp programming]]
:PROPERTIES:
:CUSTOM_ID: sec:common-lisp-programming
:END:

Links to Common Lisp books and posts are:
1. [[https://lisp-lang.org/][Common Lisp]]
2. [[https://kvardek-du.kerno.org/][Kvardek Du - Luis Oliveira]]
3. [[https://redirect.cs.umbc.edu/courses/331/resources/lisp/][Lisp Resources]]
4. [[https://redirect.cs.umbc.edu/courses/331/resources/lisp/onLisp/][On Lisp - Paul Graham]]
5. [[https://dept-info.labri.fr/~strandh/Teaching/Programmation-Symbolique/Common/Book/HTML/programmation.html][Traité de Programmation en Common Lisp]]

*** [[https://joaotavora.github.io/sly/][Sly]]
:PROPERTIES:
:CUSTOM_ID: sec:sly
:END:

Listing [[lst:configure-sly]] configures the [[info:sly#Top][Sly (info)]] Common Lisp IDE for Emacs
for use with [[http://www.sbcl.org/][Steel Bank Common Lisp (sbcl)]]:
1. It configures =sly-default-lisp= and =sly-lisp-implementations= as in the
   ~sly~ documentation string instead of in the [[info:sly#Multiple Lisps][multiple lisps (info)]] manual.
2. It does not ensure the [[info:sly#Auto-SLY][automatic connection to the lisp server (info)]] when
   opening a Common Lisp file because it does not play well with =ob-lisp=.
3. It configures searching documentation in the [[http://www.lispworks.com/documentation/HyperSpec/Front/][Common Lisp HyperSpec]] according
   to the [[info:sly#Basic customization][basic customization (info)]] manual.
Listing [[lst:slink-sel]] allows to set or get the Sly string elision length.
Finally, listing [[lst:configure-sly]] uses a technique to [[info:sly#Loading Slynk faster][load Slynk faster (info)]]
by means of a custom core file in src_emacs-lisp[:results
none]{(describe-variable 'no-littering-var-directory)}.  Listing
[[lst:sbcl-core-for-sly]] tangles to a script to dump such a [[http://www.sbcl.org/][SBCL]] core.

#+caption[Configure =sly=]:
#+caption: Configure =sly=.
#+name: lst:configure-sly
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'sly 'sly-macrostep 'sly-named-readtables)
  (with-eval-after-load 'sly
    ;; Set `sly-default-lisp' instead of `inferior-lisp-program',
    ;; because `sly' uses `inferior-lisp-program' only as a backwards
    ;; compatibility fallback option.
    ;; The warning "Value ‘sbcl’ does not match type function" is due to
    ;; the buggy `defcustom' type of `sbcl-default-lisp' in `sly.el'.
    (setopt sly-db-initial-restart-limit 10
            sly-default-lisp 'sbcl
            sly-lisp-implementations
            `((ccl (,(executable-find "ccl64")))
              (sbcl (,(executable-find "sbcl")
                     "--core"
                     ,(no-littering-expand-var-file-name "sbcl.core-for-sly")))))

    ;; (add-hook 'sly-mode-hook
    ;;           (defun on-sly-mode-hook ()
    ;;             (unless (sly-connected-p)
    ;;               (save-excursion (sly)))))

    (cond
     ((eq system-type 'darwin)
      (setq common-lisp-hyperspec-root
            "file:///usr/local/share/doc/hyperspec/HyperSpec/")
      (setq common-lisp-hyperspec-symbol-table
            (concat common-lisp-hyperspec-root "Data/Map_Sym.txt")))
     ((eq system-type 'gnu/linux)
      (setq common-lisp-hyperspec-root
            "file:///usr/share/doc/hyperspec-7.0/HyperSpec/"))
     (t (message "Default Common Lisp HyperSpec access")))

    (keymap-set sly-prefix-map "M-h" #'sly-documentation-lookup)))
#+end_src

#+caption[Get/set Sly ~slynk:*string-elision-length*~ functionality]:
#+caption: Get/set Sly ~slynk:*string-elision-length*~ functionality.
#+name: lst:slink-sel
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'sly
  (defconst slynk-command-get-sel
    "(cdr (assoc 'slynk:*string-elision-length* slynk:*slynk-pprint-bindings*))"
    "Slynk \"string elision length\" getter command.")

  (defun slynk-command-set-sel (length)
    "Slynk LENGTH \"string elision length\" setter command.
LENGTH values must be positive integers to enable or `nil' to disable elision."
    (format "(setf %s %s)" slynk-command-get-sel length))

  (defun slynk-get-sel ()
    "Get the Slynk \"string-elision-length\"."
    (cadr (sly-eval `(slynk:eval-and-grab-output ,slynk-command-get-sel))))

  ;; Most useful for Org source blocks.
  (defun slynk-set-sel (length)
    "Set the Slynk \"string-elision-length\" LENGTH.
LENGTH values must be positive integers to enable or `nil' to disable elision."
    (cadr
     (sly-eval `(slynk:eval-and-grab-output ,(slynk-command-set-sel length)))))

  ;; Most useful for interactive use.
  (defun slynk-eval-sel-command (string)
    "Evaluate the Slynk \"string-elision-length\" command STRING."
    (unless (sly-connected-p)
      (user-error "Slynk connection is not open: \"M-x sly\"?"))
    (message "Slynk string elision length is %S"
             (read (cadr (sly-eval `(slynk:eval-and-grab-output ,string))))))

  (defun slynk-get-string-elision-length ()
    "Get the Slynk \"string-elision-length\"."
    (interactive)
    (slynk-eval-sel-command slynk-command-get-sel))

  (defun slynk-set-string-elision-length (&optional length)
    "Set the Slynk \"string-elision-length\" LENGTH.
Valid LENGTH values are positive integers to set or `nil' to reset."
    (interactive "X\ Slink string elision length: ")
    (unless (or (null length) (and (integerp length) (> length 0)))
      (user-error
       "Slynk `length' must be `nil' or a positive integer (got `%S')" length))
    (slynk-eval-sel-command (slynk-command-set-sel length))))
#+end_src

#+caption[Script to dump a SBCL core for the Sly Common Lisp IDE]:
#+caption: Script to dump a SBCL core for the Sly Common Lisp IDE.
#+header: :tangle-mode (identity #o755)
#+name: lst:sbcl-core-for-sly
#+begin_src shell -n :eval never :tangle ~/bin/sbcl.core-for-sly
#!/bin/sh

sbcl <<EOF
(mapc 'require '(sb-bsd-sockets sb-posix sb-introspect sb-cltl2 asdf))
(save-lisp-and-die "sbcl.core-for-sly")
EOF

# Local Variables:
# mode: shell-script
# sh-indentation: 2
# sh-basic-offset: 2
# End:
#+end_src

*** [[https://courses.cs.northwestern.edu/325/][CS 325 AI Programming]]
:PROPERTIES:
:CUSTOM_ID: sec:cs-325-ai-programming
:END:

The [[https://courses.cs.northwestern.edu/325/][CS 325 AI Programming]] course allows to learn Common Lisp by self-study and
the page [[https://courses.cs.northwestern.edu/325/admin/lisp-setup.php][CS 325: Setting up Lisp]] gives instructions how to:
1. [[https://courses.cs.northwestern.edu/325/admin/lisp-setup.php#lisp][Download and install common lisp]].
2. [[https://courses.cs.northwestern.edu/325/admin/lisp-setup.php#quicklisp][Install Quicklisp]].
3. [[https://courses.cs.northwestern.edu/325/admin/lisp-setup.php#install-325][Install the CS325 library]].

*** [[https://www.quicklisp.org/][Quicklisp]]
:PROPERTIES:
:CUSTOM_ID: sec:quicklisp
:END:

[[https://www.quicklisp.org/][Quicklisp]] is a library manager for Common Lisp.  Listing
[[lst:download+verify-quicklisp]] downloads the [[https://www.quicklisp.org/][Quicklisp]] installation file and
verifies its signature to prevent tampering.  Listing [[lst:bootstrap-quicklisp]]
tangles to a shell script allowing to bootstrap [[https://www.quicklisp.org/][Quicklisp]] with [[http://www.sbcl.org/][SBCL]].  Listing
[[lst:quicklisp-sbclrc-file]] tangles to the a [[http://www.sbcl.org/][SBCL]] resource file with [[https://www.quicklisp.org/][Quicklisp]]
support. Listing [[lst:clone-local-projects]] shows how to make local projects out
of unpackaged projects and listing [[lst:register-load-local-projects]] shows how to
register local projects in order to load those unpackaged projects in the same
way as packaged projects.

#+caption[Download and verify =quicklisp=]:
#+caption: Download and verify =quicklisp=.
#+name: lst:download+verify-quicklisp
#+begin_src shell -n :dir ~ :results none :tangle no
curl -sS -O https://beta.quicklisp.org/quicklisp.lisp
curl -sS -O https://beta.quicklisp.org/quicklisp.lisp.asc
curl -sS -O https://beta.quicklisp.org/release-key.txt
gpg --import release-key.txt
gpg --verify quicklisp.lisp.asc quicklisp.lisp
#+end_src

#+caption[Bootstrap =quicklisp=]:
#+caption: Bootstrap =quicklisp=.
#+header: :tangle-mode (identity #o755)
#+name: lst:bootstrap-quicklisp
#+begin_src shell -n :eval never :tangle ~/bin/quicklisp-sbcl-bootstrap
#!/bin/sh

sbcl --load ~/quicklisp.lisp <<EOF
(quicklisp-quickstart:install)
(quit)
EOF

# Local Variables:
# mode: shell-script
# sh-indentation: 2
# sh-basic-offset: 2
# End:
#+end_src

#+caption[Clone local =quicklisp= projects]:
#+caption: Clone local =quicklisp= projects.
#+name: lst:clone-local-projects
#+begin_src shell -n :dir ~/quicklisp/local-projects :results none :tangle no
git clone https://gitlab.com/criesbeck/cs325.git
git clone git@github.com:ageldama/cl-state-machine.git
#+end_src

#+caption[Register and load local =quicklisp= projects with dependencies]:
#+caption: Register and load local =quicklisp= projects with dependencies.
#+name: lst:register-load-local-projects
#+begin_src lisp -n :eval never-export :results none :tangle no
;; SBCL on Darwin fails to run cl-cffi-gtk:
;; https://lisp-journey.gitlab.io/blog/gui-programming-in-common-lisp-part-3-of-5-gtk3/
;; https://www.crategus.com/books/cl-cffi-gtk/
;; https://www.crategus.com/books/cl-gtk/gtk-tutorial.html
(defun probe--local-project-directory (name)
  (some #'identity (mapcar (lambda (x)
                             (let ((*default-pathname-defaults* x))
                               (probe-file name)))
                           ql:*local-project-directories*)))

(when (probe--local-project-directory "cs325")
  (ql:register-local-projects)
  (ql:quickload "cs325")
  (ql:quickload "meta")
  (ql:quickload '("named-readtables" "try")) ;; testing requires "try".
  #-:clozure
  (ql:quickload "nodgui") ;; requires https://www.tcl.tk/software/tklib/
  (ql:quickload '("rutils" "rutilsx"))
  (ql:quickload "ucons"))

(when (probe--local-project-directory "cl-state-machine")
  (ql:quickload '("cl-state-machine" "cl-state-machine-examples"
                  "cl-state-machine-graphing" "cl-state-machine-test")))
#+end_src

#+caption: A =quicklisp= sbclrc file.
#+name: lst:quicklisp-sbclrc-file
#+begin_src lisp -n :eval never :tangle ~/.sbclrc
;;; Hey Emacs, this is my -*- lisp -*- .sbclrc file.

;;; The following lines added by ql:add-to-init-file:
#-quicklisp
(let ((quicklisp-init (merge-pathnames "quicklisp/setup.lisp"
                                       (user-homedir-pathname))))
  (when (probe-file quicklisp-init)
    (load quicklisp-init)))

;;; Load cs325.lisp to create the cs325 package.

;; (eval-when (:compile-toplevel :load-toplevel :execute)
;;   (ql:quickload "cs325")
;;   (setq *package* (find-package :cs325-user)))
#+end_src

** [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Lisp mode custom font locking for Common Lisp]]
:PROPERTIES:
:CUSTOM_ID: sec:lisp-custom-font-locking
:END:

This section implements the code described in the [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Emacs Common Lisp Font Locking]]
post.

*** [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Initialize Common Lisp custom font locking]]
:PROPERTIES:
:CUSTOM_ID: sec:cl-custom-font-locking-start
:END:

#+caption[Define faces for =Common Lisp= custom font locking]:
#+caption: Define faces for =Common Lisp= custom-font-locking.
#+name: lst:cl-custom-font-locking-faces
#+begin_src emacs-lisp -n :results silent
;;; Common Lisp custom font lock configuration.
;;; https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/

(defface cl-character-face
  '((default :inherit font-lock-constant-face))
  "The face used to highlight Common Lisp character literals.")

(defface cl-standard-function-face
  '((default :inherit font-lock-keyword-face))
  "The face used to highlight standard Common Lisp function symbols.")

(defface cl-standard-value-face
  '((default :inherit font-lock-variable-name-face))
  "The face used to highlight standard Common Lisp value symbols.")
#+end_src

#+caption[Define a =Common Lisp= function to find standard symbol names]:
#+caption: Define a =Common Lisp= function to find standard symbol names.
#+name: lst:standard-symbol-names
#+begin_src lisp -n :eval never-export :results silent :tangle no
(defun standard-symbol-names (predicate)
  (let ((symbols nil))
    (do-external-symbols (symbol :common-lisp)
      (when (funcall predicate symbol)
        (push (string-downcase (symbol-name symbol)) symbols)))
    (sort symbols #'string<)))
#+end_src

#+caption[Set Sly ~slynk:*string-elision-length*~]:
#+caption: Set Sly ~slynk:*string-elision-length*~.
#+name: lst:set-sly-sel
#+header: :wrap "src text -n"
#+begin_src emacs-lisp -n :eval never-export :exports both :tangle no
(when (and (fboundp 'sly-connected-p) (sly-connected-p))
  (and (fboundp 'slynk-set-sel) (slynk-set-sel (ash 1 14))))
#+end_src

#+caption[Set Sly ~slynk:*string-elision-length*~ result]:
#+caption: Set Sly ~slynk:*string-elision-length*~ result.
#+name: lst:set-sly-sel-result
#+RESULTS: lst:set-sly-sel
#+begin_src text -n
16384 (15 bits, #x4000)
#+end_src

*** [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Collect standard symbol function names]]
:PROPERTIES:
:CUSTOM_ID: sec:cl-function-names
:END:

#+caption[Define the =cl-function-names= variable in an =Emacs Lisp= block]:
#+caption: Use =Common Lisp= to define the =cl-function-names= variable in
#+caption: an =Emacs Lisp= source block for tangling into =user-init-file=.
#+name: lst:define-cl-function-names
#+header: :wrap "src emacs-lisp -n :results silent"
#+begin_src lisp -n :exports both :eval never-export
(format nil "(defvar~%  cl-function-names~%  '~S)~%"
        (standard-symbol-names #'fboundp))
#+end_src

#+RESULTS: lst:define-cl-function-names
#+begin_src emacs-lisp -n :results silent
(defvar
  cl-function-names
  '("*" "+" "-" "/" "/=" "1+" "1-" "<" "<=" "=" ">" ">=" "abort" "abs" "acons"
    "acos" "acosh" "add-method" "adjoin" "adjust-array" "adjustable-array-p"
    "allocate-instance" "alpha-char-p" "alphanumericp" "and" "append" "apply"
    "apropos" "apropos-list" "aref" "arithmetic-error-operands"
    "arithmetic-error-operation" "array-dimension" "array-dimensions"
    "array-displacement" "array-element-type" "array-has-fill-pointer-p"
    "array-in-bounds-p" "array-rank" "array-row-major-index" "array-total-size"
    "arrayp" "ash" "asin" "asinh" "assert" "assoc" "assoc-if" "assoc-if-not"
    "atan" "atanh" "atom" "bit" "bit-and" "bit-andc1" "bit-andc2" "bit-eqv"
    "bit-ior" "bit-nand" "bit-nor" "bit-not" "bit-orc1" "bit-orc2"
    "bit-vector-p" "bit-xor" "block" "boole" "both-case-p" "boundp" "break"
    "broadcast-stream-streams" "butlast" "byte" "byte-position" "byte-size"
    "caaaar" "caaadr" "caaar" "caadar" "caaddr" "caadr" "caar" "cadaar"
    "cadadr" "cadar" "caddar" "cadddr" "caddr" "cadr" "call-method" "car"
    "case" "catch" "ccase" "cdaaar" "cdaadr" "cdaar" "cdadar" "cdaddr" "cdadr"
    "cdar" "cddaar" "cddadr" "cddar" "cdddar" "cddddr" "cdddr" "cddr" "cdr"
    "ceiling" "cell-error-name" "cerror" "change-class" "char" "char-code"
    "char-downcase" "char-equal" "char-greaterp" "char-int" "char-lessp"
    "char-name" "char-not-equal" "char-not-greaterp" "char-not-lessp"
    "char-upcase" "char/=" "char<" "char<=" "char=" "char>" "char>="
    "character" "characterp" "check-type" "cis" "class-name" "class-of"
    "clear-input" "clear-output" "close" "clrhash" "code-char" "coerce"
    "compile" "compile-file" "compile-file-pathname" "compiled-function-p"
    "compiler-macro-function" "complement" "complex" "complexp"
    "compute-applicable-methods" "compute-restarts" "concatenate"
    "concatenated-stream-streams" "cond" "conjugate" "cons" "consp"
    "constantly" "constantp" "continue" "copy-alist" "copy-list"
    "copy-pprint-dispatch" "copy-readtable" "copy-seq" "copy-structure"
    "copy-symbol" "copy-tree" "cos" "cosh" "count" "count-if" "count-if-not"
    "ctypecase" "decf" "declaim" "decode-float" "decode-universal-time"
    "defclass" "defconstant" "defgeneric" "define-compiler-macro"
    "define-condition" "define-method-combination" "define-modify-macro"
    "define-setf-expander" "define-symbol-macro" "defmacro" "defmethod"
    "defpackage" "defparameter" "defsetf" "defstruct" "deftype" "defun"
    "defvar" "delete" "delete-duplicates" "delete-file" "delete-if"
    "delete-if-not" "delete-package" "denominator" "deposit-field" "describe"
    "describe-object" "destructuring-bind" "digit-char" "digit-char-p"
    "directory" "directory-namestring" "disassemble" "do" "do*"
    "do-all-symbols" "do-external-symbols" "do-symbols" "documentation"
    "dolist" "dotimes" "dpb" "dribble" "ecase" "echo-stream-input-stream"
    "echo-stream-output-stream" "ed" "eighth" "elt" "encode-universal-time"
    "endp" "enough-namestring" "ensure-directories-exist"
    "ensure-generic-function" "eq" "eql" "equal" "equalp" "error" "etypecase"
    "eval" "eval-when" "evenp" "every" "exp" "export" "expt" "fboundp"
    "fceiling" "fdefinition" "ffloor" "fifth" "file-author"
    "file-error-pathname" "file-length" "file-namestring" "file-position"
    "file-string-length" "file-write-date" "fill" "fill-pointer" "find"
    "find-all-symbols" "find-class" "find-if" "find-if-not" "find-method"
    "find-package" "find-restart" "find-symbol" "finish-output" "first" "flet"
    "float" "float-digits" "float-precision" "float-radix" "float-sign"
    "floatp" "floor" "fmakunbound" "force-output" "format" "formatter" "fourth"
    "fresh-line" "fround" "ftruncate" "funcall" "function" "function-keywords"
    "function-lambda-expression" "functionp" "gcd" "gensym" "gentemp" "get"
    "get-decoded-time" "get-dispatch-macro-character" "get-internal-real-time"
    "get-internal-run-time" "get-macro-character" "get-output-stream-string"
    "get-properties" "get-setf-expansion" "get-universal-time" "getf" "gethash"
    "go" "graphic-char-p" "handler-bind" "handler-case" "hash-table-count"
    "hash-table-p" "hash-table-rehash-size" "hash-table-rehash-threshold"
    "hash-table-size" "hash-table-test" "host-namestring" "identity" "if"
    "ignore-errors" "imagpart" "import" "in-package" "incf"
    "initialize-instance" "input-stream-p" "inspect" "integer-decode-float"
    "integer-length" "integerp" "interactive-stream-p" "intern" "intersection"
    "invalid-method-error" "invoke-debugger" "invoke-restart"
    "invoke-restart-interactively" "isqrt" "keywordp" "labels" "lambda" "last"
    "lcm" "ldb" "ldb-test" "ldiff" "length" "let" "let*"
    "lisp-implementation-type" "lisp-implementation-version" "list" "list*"
    "list-all-packages" "list-length" "listen" "listp" "load"
    "load-logical-pathname-translations" "load-time-value" "locally" "log"
    "logand" "logandc1" "logandc2" "logbitp" "logcount" "logeqv"
    "logical-pathname" "logical-pathname-translations" "logior" "lognand"
    "lognor" "lognot" "logorc1" "logorc2" "logtest" "logxor" "long-site-name"
    "loop" "loop-finish" "lower-case-p" "machine-instance" "machine-type"
    "machine-version" "macro-function" "macroexpand" "macroexpand-1" "macrolet"
    "make-array" "make-broadcast-stream" "make-concatenated-stream"
    "make-condition" "make-dispatch-macro-character" "make-echo-stream"
    "make-hash-table" "make-instance" "make-instances-obsolete" "make-list"
    "make-load-form" "make-load-form-saving-slots" "make-package"
    "make-pathname" "make-random-state" "make-sequence" "make-string"
    "make-string-input-stream" "make-string-output-stream" "make-symbol"
    "make-synonym-stream" "make-two-way-stream" "makunbound" "map" "map-into"
    "mapc" "mapcan" "mapcar" "mapcon" "maphash" "mapl" "maplist" "mask-field"
    "max" "member" "member-if" "member-if-not" "merge" "merge-pathnames"
    "method-combination-error" "method-qualifiers" "min" "minusp" "mismatch"
    "mod" "muffle-warning" "multiple-value-bind" "multiple-value-call"
    "multiple-value-list" "multiple-value-prog1" "multiple-value-setq"
    "name-char" "namestring" "nbutlast" "nconc" "nintersection" "ninth"
    "no-applicable-method" "no-next-method" "not" "notany" "notevery" "nreconc"
    "nreverse" "nset-difference" "nset-exclusive-or" "nstring-capitalize"
    "nstring-downcase" "nstring-upcase" "nsublis" "nsubst" "nsubst-if"
    "nsubst-if-not" "nsubstitute" "nsubstitute-if" "nsubstitute-if-not" "nth"
    "nth-value" "nthcdr" "null" "numberp" "numerator" "nunion" "oddp" "open"
    "open-stream-p" "or" "output-stream-p" "package-error-package"
    "package-name" "package-nicknames" "package-shadowing-symbols"
    "package-use-list" "package-used-by-list" "packagep" "pairlis"
    "parse-integer" "parse-namestring" "pathname" "pathname-device"
    "pathname-directory" "pathname-host" "pathname-match-p" "pathname-name"
    "pathname-type" "pathname-version" "pathnamep" "peek-char" "phase" "plusp"
    "pop" "position" "position-if" "position-if-not" "pprint" "pprint-dispatch"
    "pprint-exit-if-list-exhausted" "pprint-fill" "pprint-indent"
    "pprint-linear" "pprint-logical-block" "pprint-newline" "pprint-pop"
    "pprint-tab" "pprint-tabular" "prin1" "prin1-to-string" "princ"
    "princ-to-string" "print" "print-not-readable-object" "print-object"
    "print-unreadable-object" "probe-file" "proclaim" "prog" "prog*" "prog1"
    "prog2" "progn" "progv" "provide" "psetf" "psetq" "push" "pushnew" "quote"
    "random" "random-state-p" "rassoc" "rassoc-if" "rassoc-if-not" "rational"
    "rationalize" "rationalp" "read" "read-byte" "read-char"
    "read-char-no-hang" "read-delimited-list" "read-from-string" "read-line"
    "read-preserving-whitespace" "read-sequence" "readtable-case" "readtablep"
    "realp" "realpart" "reduce" "reinitialize-instance" "rem" "remf" "remhash"
    "remove" "remove-duplicates" "remove-if" "remove-if-not" "remove-method"
    "remprop" "rename-file" "rename-package" "replace" "require" "rest"
    "restart-bind" "restart-case" "restart-name" "return" "return-from"
    "revappend" "reverse" "room" "rotatef" "round" "row-major-aref" "rplaca"
    "rplacd" "sbit" "scale-float" "schar" "search" "second" "set"
    "set-difference" "set-dispatch-macro-character" "set-exclusive-or"
    "set-macro-character" "set-pprint-dispatch" "set-syntax-from-char" "setf"
    "setq" "seventh" "shadow" "shadowing-import" "shared-initialize" "shiftf"
    "short-site-name" "signal" "signum" "simple-bit-vector-p"
    "simple-condition-format-arguments" "simple-condition-format-control"
    "simple-string-p" "simple-vector-p" "sin" "sinh" "sixth" "sleep"
    "slot-boundp" "slot-exists-p" "slot-makunbound" "slot-missing"
    "slot-unbound" "slot-value" "software-type" "software-version" "some"
    "sort" "special-operator-p" "sqrt" "stable-sort" "standard-char-p" "step"
    "store-value" "stream-element-type" "stream-error-stream"
    "stream-external-format" "streamp" "string" "string-capitalize"
    "string-downcase" "string-equal" "string-greaterp" "string-left-trim"
    "string-lessp" "string-not-equal" "string-not-greaterp" "string-not-lessp"
    "string-right-trim" "string-trim" "string-upcase" "string/=" "string<"
    "string<=" "string=" "string>" "string>=" "stringp" "sublis" "subseq"
    "subsetp" "subst" "subst-if" "subst-if-not" "substitute" "substitute-if"
    "substitute-if-not" "subtypep" "svref" "sxhash" "symbol-function"
    "symbol-macrolet" "symbol-name" "symbol-package" "symbol-plist"
    "symbol-value" "symbolp" "synonym-stream-symbol" "tagbody" "tailp" "tan"
    "tanh" "tenth" "terpri" "the" "third" "throw" "time" "trace"
    "translate-logical-pathname" "translate-pathname" "tree-equal" "truename"
    "truncate" "two-way-stream-input-stream" "two-way-stream-output-stream"
    "type-error-datum" "type-error-expected-type" "type-of" "typecase" "typep"
    "unbound-slot-instance" "unexport" "unintern" "union" "unless"
    "unread-char" "untrace" "unuse-package" "unwind-protect"
    "update-instance-for-different-class" "update-instance-for-redefined-class"
    "upgraded-array-element-type" "upgraded-complex-part-type" "upper-case-p"
    "use-package" "use-value" "user-homedir-pathname" "values" "values-list"
    "vector" "vector-pop" "vector-push" "vector-push-extend" "vectorp" "warn"
    "when" "wild-pathname-p" "with-accessors" "with-compilation-unit"
    "with-condition-restarts" "with-hash-table-iterator"
    "with-input-from-string" "with-open-file" "with-open-stream"
    "with-output-to-string" "with-package-iterator" "with-simple-restart"
    "with-slots" "with-standard-io-syntax" "write" "write-byte" "write-char"
    "write-line" "write-sequence" "write-string" "write-to-string" "y-or-n-p"
    "yes-or-no-p" "zerop"))
#+end_src

*** [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Collect standard symbol value names]]
:PROPERTIES:
:CUSTOM_ID: sec:cl-value-names
:END:

#+caption[Define the =cl-variable-names= variable in an =Emacs Lisp= block]:
#+caption: Use =Common Lisp= to define the =cl-variable-names= variable in
#+caption: an =Emacs Lisp= source block for tangling into =user-init-file=.
#+name: lst:define-cl-value-names
#+header: :wrap "src emacs-lisp -n :results silent"
#+begin_src lisp -n :exports both :eval never-export
(format nil "(defvar~%  cl-value-names~%  '~S)~%"
        (standard-symbol-names #'boundp))
#+end_src

#+RESULTS: lst:define-cl-value-names
#+begin_src emacs-lisp -n :results silent
(defvar
  cl-value-names
  '("*" "**" "***" "*break-on-signals*" "*compile-file-pathname*"
    "*compile-file-truename*" "*compile-print*" "*compile-verbose*"
    "*debug-io*" "*debugger-hook*" "*default-pathname-defaults*"
    "*error-output*" "*features*" "*gensym-counter*" "*load-pathname*"
    "*load-print*" "*load-truename*" "*load-verbose*" "*macroexpand-hook*"
    "*modules*" "*package*" "*print-array*" "*print-base*" "*print-case*"
    "*print-circle*" "*print-escape*" "*print-gensym*" "*print-length*"
    "*print-level*" "*print-lines*" "*print-miser-width*"
    "*print-pprint-dispatch*" "*print-pretty*" "*print-radix*"
    "*print-readably*" "*print-right-margin*" "*query-io*" "*random-state*"
    "*read-base*" "*read-default-float-format*" "*read-eval*" "*read-suppress*"
    "*readtable*" "*standard-input*" "*standard-output*" "*terminal-io*"
    "*trace-output*" "+" "++" "+++" "-" "/" "//" "///" "array-dimension-limit"
    "array-rank-limit" "array-total-size-limit" "boole-1" "boole-2" "boole-and"
    "boole-andc1" "boole-andc2" "boole-c1" "boole-c2" "boole-clr" "boole-eqv"
    "boole-ior" "boole-nand" "boole-nor" "boole-orc1" "boole-orc2" "boole-set"
    "boole-xor" "call-arguments-limit" "char-code-limit" "double-float-epsilon"
    "double-float-negative-epsilon" "internal-time-units-per-second"
    "lambda-list-keywords" "lambda-parameters-limit"
    "least-negative-double-float" "least-negative-long-float"
    "least-negative-normalized-double-float"
    "least-negative-normalized-long-float"
    "least-negative-normalized-short-float"
    "least-negative-normalized-single-float" "least-negative-short-float"
    "least-negative-single-float" "least-positive-double-float"
    "least-positive-long-float" "least-positive-normalized-double-float"
    "least-positive-normalized-long-float"
    "least-positive-normalized-short-float"
    "least-positive-normalized-single-float" "least-positive-short-float"
    "least-positive-single-float" "long-float-epsilon"
    "long-float-negative-epsilon" "most-negative-double-float"
    "most-negative-fixnum" "most-negative-long-float"
    "most-negative-short-float" "most-negative-single-float"
    "most-positive-double-float" "most-positive-fixnum"
    "most-positive-long-float" "most-positive-short-float"
    "most-positive-single-float" "multiple-values-limit" "nil" "pi"
    "short-float-epsilon" "short-float-negative-epsilon" "single-float-epsilon"
    "single-float-negative-epsilon" "t"))
#+end_src

*** [[https://www.n16f.net/blog/custom-font-lock-configuration-in-emacs/][Finalize Common Lisp custom font locking]]
:PROPERTIES:
:CUSTOM_ID: sec:cl-custom-font-locking-final
:END:

#+caption[Finalize =Common Lisp= custom font locking]:
#+caption: Finalize =Common Lisp= custom font locking.
#+name: lst:finalize-cl-custom-font-locking
#+begin_src emacs-lisp -n :results silent
(defvar cl-font-lock-keywords
  (let* ((character-re (concat "#\\\\" lisp-mode-symbol-regexp "\\_>"))
         (function-re (concat "(" (regexp-opt cl-function-names t) "\\_>"))
         (value-re (regexp-opt cl-value-names 'symbols)))
    `((,character-re . 'cl-character-face)
      (,function-re
       (1 'cl-standard-function-face))
      (,value-re . 'cl-standard-value-face))))

(defvar cl-font-lock-defaults
  '((cl-font-lock-keywords)
    nil                                 ; enable syntaxic highlighting
    t                                   ; case insensitive highlighting
    nil                                 ; use the lisp-mode syntax table
    (font-lock-mark-block-function . mark-defun)
    (font-lock-extra-managed-props help-echo)
    (font-lock-syntactic-face-function
     . lisp-font-lock-syntactic-face-function)))

(defun cl-init-lisp-font-lock ()
  "Hook to initialize Common Lisp font locking."
  (setq font-lock-defaults cl-font-lock-defaults))

(add-hook 'lisp-mode-hook 'cl-init-lisp-font-lock)
#+end_src

** [[info:eintr#Top][Emacs Lisp Programming (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:emacs-lisp-programming
:END:

Here is a list of links describing how to program and debug [[info:elisp#Top][Emacs Lisp (info)]] code:
1. [[https://www.masteringemacs.org/article/evaluating-elisp-emacs][Evaluating Elisp in Emacs]]
2. [[https://endlessparentheses.com/debugging-emacs-lisp-part-1-earn-your-independence.html][Debugging Elisp Part 1: Earn your independence]]
3. [[https://endlessparentheses.com/debugging-elisp-part-2-advanced-topics.html][Debugging Elisp Part 2: Advanced topics]]
4. [[http://xahlee.info/talk_show/xah_talk_show_2022-01-20.html][Xah talk show: Elisp coding: xah-add-space-after-comma]]
5. [[http://xahlee.info/talk_show/xah_talk_show_2022-01-22.html][Xah talk show: Elisp coding: narrow-to-region, sort-lines, hilight-unicode]]

Ref. [cite:@Monnier.ACM-PL.4.1] exposes the evolution of Emacs Lisp and explains
important Emacs Lisp idioms.

*** [[info:emacs#Bug Reference][Bug Reference Mode (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:bug-reference-mode
:END:

Listing [[lst:bug-reference-mode]] configures ~bug-reference-mode~ for use with the
[[https://debbugs.gnu.org/][GNU Bug Tracker]].

#+caption[Setup ~bug-reference-mode~]:
#+caption: Setup ~bug-reference-mode~.
#+name: lst:bug-reference-mode
#+begin_src emacs-lisp -n :results silent
;; (info "(debbugs) Top")
;; (info "(emacs) Bug Reference")
(ensure-package-installation 'debbugs)
(defvar bug-reference-url-format
  "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=%s"
  "Format to use `gnu-debbugs' URL.")
(put 'bug-reference-mode 'safe-local-variable 'booleanp)
#+end_src

*** [[info:elisp#Debugging][Debugging Emacs Lisp (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:debugging
:END:

GAV: I fail to instrument the functions from the [[https://www.emacswiki.org/emacs/SourceLevelDebugger][source level debugger (edebug)]]
wiki entry as in [[info:elisp#Edebug][Edebug (info)]].

*** [[https://www.masteringemacs.org/article/evaluating-elisp-emacs][Evaluating Elisp in Emacs]]
:PROPERTIES:
:CUSTOM_ID: sec:elisp-evaluation
:END:

Listing [[lst:setup-ielm][setup ielm]] configures the [[https://wikemacs.org/wiki/IELM][Interactive Emacs Lisp Mode]] for better
interoperability with [[https://smartparens.readthedocs.io/en/latest/][smartparens]]: get help on the key bindings by means of
src_emacs-lisp[:results none]{(describe-function 'ielm)}.

#+caption[Setup =ielm=]:
#+caption: Setup =ielm=.
#+name: lst:setup-ielm
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ielm
  (setopt ielm-dynamic-return nil))
#+end_src

*** [[http://yummymelon.com/devnull/writing-better-elisp-docstrings.html][Writing Better Elisp Docstrings]]
:PROPERTIES:
:CUSTOM_ID: sec:describe-function-at-point
:END:

#+caption[Describe Elisp function at point]:
#+caption: Describe Elisp function at point.
#+name: lst:describe-function-at-point
#+begin_src emacs-lisp -n :results silent
;; Stolen from Charles Choi:
;; http://yummymelon.com/devnull/writing-better-elisp-docstrings.html
;; GAV: Org changes the semantics of calling `beginning-of-defun'.
(defun describe-function-at-point ()
  "Call `describe-function' on the Elisp function at point.
Switch temporarily from `org-mode' to `text-mode', since `org-mode'
changes the semantics of calling `beginning-of-defun'."
  (interactive)
  (let ((mode major-mode))
    (when (eq major-mode 'org-mode)
      (text-mode))
    (save-excursion
      (beginning-of-defun)
      (forward-char)
      (forward-sexp 2)
      (let ((end-point (point)))
        (backward-sexp)
        (let* ((fn-name (buffer-substring (point) end-point))
               (interned (intern-soft fn-name)))
          (if interned
              (describe-function interned)
            (message "Can't find function at point")))))
    (when (eq mode 'org-mode)
      (org-mode))))

(with-eval-after-load 'org-mode
  (keymap-set org-mode-map "C-c d" #'describe-function-at-point))
(with-eval-after-load 'emacs-lisp-mode
  (keymap-set emacs-lisp-mode-map "C-c d" #'describe-function-at-point))
#+end_src

** [[https://go.dev/][Go Programming]]
:PROPERTIES:
:CUSTOM_ID: sec:go-programming
:END:

Links for further investigation are:
1. [[https://gobyexample.com/][Go by example]] is a showcase of short examples with explanations.

#+caption[Setup Go programming]:
#+caption: Setup Go programming.
#+name: lst:setup-go
#+begin_src emacs-lisp -n :results silent
(when (featurep 'treesit)
  (setopt go-ts-mode-indent-offset 2)
  (add-hook 'go-ts-mode-hook (lambda ()
                               (setq-local tab-width 2)))
  (add-to-list 'auto-mode-alist `(,(rx ".go" eos) . go-ts-mode)))
#+end_src

** [[https://www.seas.upenn.edu/~chaoliu/2017/09/01/python-programming-in-emacs/][Python programming]]
:PROPERTIES:
:CUSTOM_ID: sec:python-programming
:END:

The [[https://www.emacswiki.org/emacs/PythonProgrammingInEmacs][Python Programming in Emacs]] wiki page lists options to enhance Emacs's
built-in ~python-mode~. Here, the focus is on one Emacs package and three Python
packages:
1. [[#sec:eglot][Eglot - Emacs polyGLOT: a builtin LSP client since Emacs-29.1]] and its author
   (who is a prolific Common Lisp and Emacs Lisp programmer) has also
   contributed to other parts of Emacs.
2. [[https://jedi.readthedocs.io/en/latest/][Jedi]] is a static analysis tool for Python that is typically used in plugins
   for editors or integrated development environments.  Jedi has a focus on
   autocompletion and object definition lookup functionality.
3. Nowadays, [[https://github.com/charliermarsh/ruff#readme][Ruff]] is the fastest Python linter and a replacement for [[https://flake8.pycqa.org/en/latest/][Flake8]] with
   a variety of its plugins.  [[https://notes.crmarsh.com/][Charlie Marsh]] explains why he started [[https://pypi.org/project/ruff/][Ruff]] in the
   post [[https://notes.crmarsh.com/python-tooling-could-be-much-much-faster][Python tooling could be much faster]].
4. [[https://github.com/python-lsp/python-lsp-server#readme][Python LSP Server]] is in my opinion the most complete [[https://en.wikipedia.org/wiki/Language_Server_Protocol][Language Server Protocol]]
   implementation for Python and it handles [[https://github.com/charliermarsh/ruff#readme][Ruff]] thanks to the [[https://github.com/python-lsp/python-lsp-ruff][python-lsp-ruff]]
   plugin.
# 5. [[https://github.com/astoff/code-cells.el#readme][Code-cells]] allows to edit [[https://ipython.org/notebook.html][IPython or Jupyter notebooks]] in Emacs with help
#    from either [[https://github.com/mwouts/jupytext][Jupytext]] or [[https://pandoc.org/][Pandoc]].

Here are links covering how to integrate Emacs, Python and a Python LSP
server, before plunging into the configuration steps:
1. [[https://taingram.org/blog/emacs-lsp-ide.html][Building Your Own Emacs IDE with LSP]]
2. [[https://rgoswami.me/posts/emacs-lang-servers/][Doom Emacs and Language Servers]]
3. [[https://ddavis.io/posts/eglot-python-ide/][Eglot based Emacs Python IDE]]
4. [[https://www.mattduck.com/lsp-python-getting-started.html][Getting started with lsp-mode for Python]]
5. [[https://ddavis.io/posts/python-emacs-3/][Python & Emacs, Take 3]]
6. [[https://ddavis.io/posts/emacs-python-lsp/][Python with Emacs: py(v)env and lsp-mode]]

Here are links to Python programming background videos:
1. [[yt:T-TwcmT6Rcw][Dataclasses: The Code Generator to End All Code Generators - Raymond Hettinger]]
2. [[yt:p33CVV29OG8][Modern Dictionaries - Raymond Hettinger]]
3. [[yt:HTLu2DFOdTg][Python's Class Development Kit - Raymond Hettinger]]
4. [[yt:uL_kmagVKFQ][The Big Leap of Python-3.13 - Lukasz Langa]]
5. [[yt:UANN2Eu6ZnM][The Mental Game of Python - Raymond Hettinger]]
6. [[yt:Bv25Dwe84g0][Thinking about Concurrency - Raymond Hettinger]]
7. [[yt:0kXaLh8Fz3k][Thinking outside the GIL with AsyncIO and MultiProcessing - John Reese]]
8. [[yt:bZAsSzzk0E][What can't WebAssembly do? - Katie Bell]]

*** [[https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/progmodes/python.el][Python-mode]]
:PROPERTIES:
:CUSTOM_ID: sec:python-mode
:END:

Listing [[lst:setup-python-mode][setup Python mode]] selects a common Python interpreter in a virtual
environment for use in =python-mode= and =ob-python=.  The [[https://github.com/pythonic-emacs/pythonic#readme][pythonic]], [[https://github.com/jorgenschaefer/pyvenv#readme][pyvenv]], and
[[https://github.com/jorgenschaefer/pyvenv#readme][pyvenv]] packages allow to handle Python virtual environments within Emacs.  The
[[https://github.com/pyenv/pyenv][pyenv]] package provides support to work with [[https://github.com/pyenv/pyenv#readme][pyenv]] (eventually with
[[https://github.com/pyenv/pyenv-virtualenv#readme][pyenv-virtualenv]]) to select between different python versions (eventually each
with different environments).  In the end, all those packages do is to set
=python-shell-virtualenv-root= (in case of [[https://github.com/pyenv/pyenv#readme][pyenv]] and [[https://github.com/pythonic-emacs/pythonic#readme][pythonic]]) or tweak the
environment variables and restart the relevant Python child processes (in case
of [[https://github.com/jorgenschaefer/pyvenv#readme][pyvenv]]).  Therefore, I replace those packages with listing [[lst:access-pyenv][access pyenv]] and
[[lst:select-python-virtual-environment][select a Python interpreter in a virtual environment]] to set
=python-shell-virtualenv-root= from within Emacs.

Install [[https://github.com/PyCQA/isort#readme][isort]] and [[https://github.com/PyCQA/pyflakes#readme][pyflakes]] to enable adding, removing, sorting, and fixing
import statements in [[https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/progmodes/python.el][Python-mode]], see the end of the commentary
src_emacs-lisp[:results none]{(find-library "python")} section.

Listing [[lst:pyproject-toml-kickoff][kickoff pyproject.toml proposal]] facilitates dropping a [[https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml][pyproject.toml]]
file into Python projects which anyhow should switch to using a [[https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml][pyproject.toml]]
file as explained in the post [[https://bbc.github.io/cloudfit-public-docs/packaging/this_way_up.html][This Way Up: A Bottom-Up Look At Python Packaging]].
The [[https://packaging.python.org/en/latest/tutorials/packaging-projects/][packaging Python projects tutorial]] and the [[https://github.com/pypa/sampleproject][Python sample project]] walk you
through the process of writing a [[https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml][pyproject.toml]] file.  [[https://github.com/charliermarsh/ruff#does-ruff-support-numpy--or-google-style-docstrings][Ruff docstring setup]]
explains how to setup documentation string checking in the [[https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml][pyproject.toml]] file.

Finally, listing [[lst:ruff-nocolor][ruff-nocolor]] pipes the =stdout= output of the [[https://pypi.org/project/ruff/][ruff]] executable
through =cat= to remove escape sequences.

#+caption[Setup Python mode with =ob-python=]:
#+caption: Setup Python mode with =ob-python=.
#+name: lst:setup-python-mode
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'ob-python
  (setopt org-babel-python-command (concat (or (executable-find "python3")
                                               (executable-find "python"))
                                           " -E")))

(with-eval-after-load 'python
  (setopt python-indent-guess-indent-offset nil
          python-shell-completion-native-disabled-interpreters '("ipython3"
                                                                 "pypy")
          python-shell-interpreter (or (executable-find "python3")
                                       (executable-find "python"))
          python-shell-interpreter-args "-E -i"
          python-check-command (executable-find "ruff-nocolor")
          python-flymake-command (list (executable-find "ruff-nocolor")
                                       "--stdin-filename" "stdin" "-")))
#+end_src

#+caption[Access =pyenv=]:
#+caption: Access =pyenv=.
#+name: lst:access-pyenv
#+begin_src emacs-lisp -n :results silent
(when (executable-find "pyenv")
  (defun pyenv-full-path (version)
    "Return the full path for VERSION."
    (unless (string= version "system")
      (concat (pyenv-root) (file-name-as-directory "versions") version)))

  (defun pyenv-root ()
    "Return \"pyenv root\" as a directory."
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code "pyenv" "root")
      (if (= 0 exit-code)
          (file-name-as-directory (string-trim output))
        (error "%s" (string-trim output)))))

  (defun pyenv-version-name ()
    "Return \"pyenv version-name\"."
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code "pyenv" "version-name")
      (if (= 0 exit-code)
          (string-trim output)
        (error "%s" (string-trim output)))))

  (defun pyenv-versions ()
    "Return \"pyenv versions --bare --skip-aliases\" as a list.
Complete the result with \"system\"."
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code
         "pyenv" "versions" "--bare" "--skip-aliases")
      (if (= 0 exit-code)
          (cons "system" (split-string output))
        (error "%s" (string-trim output)))))

  (defun pyenv-virtualenvs ()
    "Return \"pyenv virtualenvs --bare --skip-aliases\" as a list."
    (cl-destructuring-bind (exit-code output)
        (shell-command-with-exit-code
         "pyenv" "virtualenvs" "--bare" "--skip-aliases")
      (if (= 0 exit-code)
          (split-string output)
        (error "%s" (string-trim output))))))
#+end_src

#+caption[Select the Python virtual environment]:
#+caption: Select the Python virtual environment.
#+name: lst:select-python-virtual-environment
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'python
  (when (cl-every #'fboundp '(pyenv-full-path
                              pyenv-version-name
                              pyenv-versions
                              pyenv-virtualenvs))
    (setq python-shell-virtualenv-root
          (pyenv-full-path (or (pyenv-version-name)
                               (car (pyenv-virtualenvs))
                               (car (pyenv-versions)))))
    (message "Now `python-shell-virtualenv-root' equals %S"
             python-shell-virtualenv-root)

    (defun set-python-shell-virtualenv-root-to-pyenv-version ()
      "Set `python-shell-virtual-env-root' to a pyenv version."
      (interactive)
      (let* ((version-name (pyenv-version-name))
             (prompt (format "pyenv version (%s): " version-name))
             (choices (pyenv-versions))
             (version (completing-read prompt choices nil 'require-match)))
        (unless (string= version-name version)
          (setq python-shell-virtualenv-root (pyenv-full-path version))
          (setenv "PYENV_VERSION" version))
        (message "Now `python-shell-virtualenv-root' equals %S"
                 python-shell-virtualenv-root)))

    (defun set-python-shell-virtualenv-root-to-pyenv-virtualenv ()
      "Set `python-shell-virtual-env-root' to a pyenv virtualenv."
      (interactive)
      (let* ((version-name (pyenv-version-name))
             (prompt (format "pyenv virtualenv (%s): " version-name))
             (choices (pyenv-virtualenvs))
             (version (completing-read prompt choices nil 'require-match)))
        (unless (string= version-name version)
          (setq python-shell-virtualenv-root (pyenv-full-path version))
          (setenv "PYENV_VERSION" version))
        (message "Now `python-shell-virtualenv-root' equals %S"
                 python-shell-virtualenv-root)))))
#+end_src

#+caption[Kickoff =pyproject.toml= proposal]:
#+caption: Kickoff =pyproject.toml= proposal.
#+name: lst:pyproject-toml-kickoff
#+begin_src toml -n :tangle pyproject.toml
# See:
# https://docs.astral.sh/ruff/configuration/
# https://pycqa.github.io/isort/docs/configuration/black_compatibility.html
# https://setuptools.pypa.io/en/latest/userguide/pyproject_config.html

[tool.black]
line-length = 88

[tool.isort]
profile = "black"

[tool.ruff]
line-length = 88
select = [
  "ARG", # flake8-unused-arguments
  "B",   # flake8-bugbear
  "C",   # mccabe
  "C4",  # flake8-comprehensions
  "E",   # pycodestyle
  "D",   # pydocstyle
  "F",   # pyflakes
  "UP",  # pyupgrade
  "W",   # pycodestyle
]
ignore = [
  "B905", # `zip()` without an explicit `strict=` parameter
  "D202", # no blank lines allowed after function docstring
]

[tool.ruff.mccabe]
max-complexity = 15

[tool.ruff.pydocstyle]
convention = "numpy"

# Local Variables:
# mode: conf-toml-mode
# End:
#+end_src

#+caption[Wrap =ruff= to remove color from text output]:
#+caption: Wrap =ruff= to remove color from text output.
#+header: :tangle-mode (identity #o755)
#+name: lst:ruff-nocolor
#+begin_src shell -n :eval never :tangle ~/bin/ruff-nocolor
#!/bin/sh

ruff "$@" | cat

# Local Variables:
# mode: shell-script
# sh-indentation: 2
# sh-basic-offset: 2
# End:
#+end_src

*** [[https://pip.pypa.io/en/stable/][Package Installer for Python]]
:PROPERTIES:
:CUSTOM_ID: sec:pip-python
:header-args: :eval never-export
:END:

Listing [[lst:shell-pip-index-versions]] are is an example of invoking [[https://pip.pypa.io/en/stable/][pip]] in an
=org-mode= =shell= source block with its results in listing
[[lst:shell-pip-index-versions-results]].  Listing [[lst:pip-pypi-options]],
[[lst:pip-list-outdated]], [[lst:pip-upgrade-maybe]] allow to upgrade outdated Python
packages.

#+caption[Show how to use =pip index versions=]:
#+caption: Show how to use =pip index versions=.
#+header: :wrap "src text -n"
#+name: lst:shell-pip-index-versions
#+begin_src shell -n :exports both :results verbatim
# WARNING: "pip index" is currently an experimental command.
pip index versions circular-buffer --no-color
#+end_src

#+caption[The result of =pip index versions=]:
#+caption: The result of =pip index versions=.
#+name: lst:shell-pip-index-versions-results
#+RESULTS: lst:shell-pip-index-versions
#+begin_src text -n
circular-buffer (0.2.0)
Available versions: 0.2.0, 0.1.1, 0.1.0
#+end_src

#+caption[Emacs client "Package Installer for Python" and "PyPI" options]:
#+caption: Emacs client "Package Installer for Python" and "PyPI" options.
#+name: lst:pip-pypi-options
#+begin_src emacs-lisp -n :results silent
(defgroup pip nil
  "Client for accessing the \"Package Installer for Python\" and \"PyPI\"."
  :group 'applications)

(defcustom pip-frozen-packages nil
  "Frozen Python packages."
  :group 'pip
  :type '(repeat string))

;; Updating "docutils" may require a compatible "Sphinx" release.
;; (setopt pip-frozen-packages '("docutils"))
#+end_src

#+caption[Emacs interface to list outdated Python packages]:
#+caption: Emacs interface to list outdated Python packages.
#+name: lst:pip-list-outdated
#+begin_src emacs-lisp -n :results silent
(defvar pip-outdated-packages nil
  "Outdated Python packages.")

(defun pip--list-outdated-sentinel (process _event)
  "Sentinel function for when the `pip-list-outdated' PROCESS succeeds."
  (when (and (eq (process-status process) 'exit)
             (zerop (process-exit-status process))
             (buffer-live-p (process-buffer process)))
    (with-current-buffer (process-buffer process)
      (goto-char (point-min))
      (setq pip-outdated-packages
            (json-parse-buffer :array-type 'list :object-type 'alist))
      (let ((alists pip-outdated-packages))
        (while alists
          (setcdr (assq 'name (car alists))
                  (string-replace "_" "-" (alist-get 'name (car alists))))
          (setq alists (cdr alists))))
      (kill-buffer)
      (describe-variable 'pip-outdated-packages)
      (message "Calling `%S' succeeded" #'pip-list-outdated))))

(defun pip-list-outdated ()
  "Save the outdated Python packages in `pip-outdated-packages'.

This invokes an asynchronous process and finishes with a message."
  (interactive)
  (let ((content '("pip" "list" "--outdated" "--format" "json")))
    (make-process
     :name "pip-list-outdated"
     :buffer (generate-new-buffer-name "*pip-list-outdated-output*")
     :command content
     :sentinel #'pip--list-outdated-sentinel)
    (message "Running `%s' asynchronously" (string-join content " "))))
#+end_src

#+caption[Emacs interface to upgrade outdated unfrozen Python packages]:
#+caption: Emacs interface to upgrade outdated unfrozen Python packages.
#+name: lst:pip-upgrade-maybe
#+begin_src emacs-lisp :results silent
(defun pip--upgrade-maybe-sentinel (process _event)
  "Sentinel function for when the `pip-upgrade-maybe' PROCESS succeeds."
  (when (and (eq (process-status process) 'exit)
             (buffer-live-p (process-buffer process)))
    (display-buffer (process-buffer process))))

(defun pip-upgrade-maybe ()
  "Install the latest version of outdated packages unless they are frozen.

This invokes an asynchronous process and finishes with displaying the process
buffer to check whether upgrading has made the dependencies incompatible."
  (interactive)
  (let (found)
    (dolist (alist pip-outdated-packages found)
      (let ((name (alist-get 'name alist))
            (latest_version (alist-get 'latest_version alist)))
        (unless (member name pip-frozen-packages)
          (push (format "%s==%s" name latest_version) found))))
    (if (consp found)
        (let ((content
               `("pip" "install" "--progress-bar" "off" ,@(nreverse found))))
          (make-process
           :name "pip-upgrade-maybe"
           :buffer (generate-new-buffer-name "*pip-upgrade-maybe*")
           :command content
           :sentinel #'pip--upgrade-maybe-sentinel)
          (message "Running `%s' asynchronously" (string-join content " ")))
      (message "`pip-upgrade-maybe' found no packages to install"))))
#+end_src

*** [[https://github.com/joaotavora/eglot][Eglot]] for [[https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/progmodes/python.el][python-mode]]
:PROPERTIES:
:CUSTOM_ID: sec:eglot-python
:END:

Listing [[lst:configure-eglot+pylsp-ruff]] configures [[https://github.com/joaotavora/eglot][eglot]] for [[https://www.python.org][Python]] using the
[[https://github.com/python-lsp/python-lsp-server][python-lsp-server]] with the [[https://github.com/python-lsp/python-lsp-ruff#readme][pylsp-ruff]] plugin for the easiest way to let
[[https://github.com/python-lsp/python-lsp-server][python-lsp-server]] use [[https://pypi.org/project/ruff/][Ruff]]. It is better to uninstall the Python packages
[[https://github.com/hhatto/autopep8#readme][autopep8]], [[https://github.com/PyCQA/flake8][flake8]], [[https://github.com/PyCQA/pydocstyle#readme][pydocstyle]], [[https://github.com/PyCQA/pylint#readme][pylint]], and [[https://github.com/python-rope/rope#readme][rope]].

Listing [[lst:eglot-directory-variables-for-python]] shows a proper [[info:emacs#Directory Variables][.dir-locals.el]]
file in the root directory of any [[https://www.python.org][Python]] project to start [[https://github.com/joaotavora/eglot][eglot]] automatically
according to the configuration in listing [[lst:eglot-maybe-ensure]].

Type {{{kbd(M-x eglot-show-workspace-configuration)}}} to dump a =JSON=
representation of src_emacs-lisp[:results none]{(describe-variable
'eglot-workspace-configuration)} for debugging.

#+caption[Configure =eglot= with =python-lsp-ruff=]:
#+caption: Configure =eglot= with =python-lsp-ruff=.
#+name: lst:configure-eglot+pylsp-ruff
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'eglot
  (setq-default
   eglot-workspace-configuration
   ;; Enable the `:pylsp_ruff' plugin and ensure to uninstall the
   ;; `:flake8', `:mccabe', and `:pycodestye' plugins.
   '(:pylsp (:plugins
             (:pylsp_ruff
              (:enabled t)
              :jedi
              (:auto_import_modules ["numpy"])
              :jedi_completion
              (:cache_for ["astropy"]))))))
#+end_src

#+caption[A =.dir-locals.el= proposal to launch =eglot= automatically]:
#+caption: A =.dir-locals.el= file proposal for Python projects or Org-mode
#+caption: projects tangling Python files to launch =eglot= automatically.
#+name: lst:eglot-directory-variables-for-python
#+begin_src emacs-lisp -n :eval never :tangle dir-locals.el
;; A .dir-locals.el file proposal in the root of any
;; Python project or Org-mode project tangling Python files
;; to launch eglot automatically.
;; Ensure to enable the pylsp_ruff plugin.
;; Ensure to uninstall the flake8, mccabe, and pycodestyle Python packages.
((nil  ;; nil, since Emacs-29.1 filters out irrelevant variable names.
  . ((eglot-workspace-configuration
      . (:pylsp (:plugins
                 (:pylsp_ruff
                  (:enabled t)
                  :jedi
                  (:auto_import_modules ["numpy"])
                  :jedi_completion
                  (:cache_for ["astropy"]))))))))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Eglot related key bindings]:
#+caption: Eglot related key-bindings.
#+name: tab:eglot-related-key-bindings
|-------------------------+----------------+------------------|
| command                 | key map        | keys             |
|-------------------------+----------------+------------------|
| xref-find-definition    | global-map     | {{{kbd(M-.)}}}   |
| xref-pop                | global-map     | {{{kbd(M-\,)}}}  |
| flymake-goto-next-error | eglot-mode-map | {{{kbd(C-c n)}}} |
| flymake-goto-prev-error | eglot-mode-map | {{{kbd(C-c p)}}} |
| eglot-rename            | eglot-mode-map | {{{kbd(C-c r)}}} |
| eldoc-doc-buffer        | eglot-mode-map | {{{kbd(C-h .)}}} |
|-------------------------+----------------+------------------|

*** [[https://jedi.readthedocs.io/en/latest/][Jedi]]
:PROPERTIES:
:CUSTOM_ID: sec:jedi
:END:

Listing [[lst:example-py]] is a [[https://www.python.org][Python]] example to test whether [[https://jedi.readthedocs.io/en/latest/][jedi]] in combination
with [[https://github.com/joaotavora/eglot][eglot]] works when coding for instance [[https://numpy.org/][numpy]] universal functions.

#+caption[Tangle the =example.py= file]:
#+caption: Tangle the =example.py= file.
#+name: lst:example-py
#+begin_src python -n :tangle example.py
import numpy
import astropy.units as apu

a = numpy.arange(0, 11)
a = numpy.linspace(0, 10, num=11)
a = numpy.arccos(a)
q = apu.Quantity(a, apu.meter)
print(q)
#+end_src

*** [[https://github.com/astoff/code-cells.el#readme][Code-cells]]                                                     :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:code-cells
:END:

[[https://github.com/astoff/code-cells.el#readme][Code-cells]] allows to edit [[https://ipython.org/notebook.html][IPython or Jupyter notebooks]] in Emacs with help from
either [[https://github.com/mwouts/jupytext][Jupytext]] or [[https://pandoc.org/][Pandoc]] to translate between the [[https://nbformat.readthedocs.io/en/latest/][ipynb]] format and different
plain text formats.  Sofar, I have used [[https://github.com/astoff/code-cells.el#readme][code-cells]] to open [[https://nbformat.readthedocs.io/en/latest/][ipynb]] notebooks with
{{{kbd(C-x C-f)}}} in Emacs for viewing.  Listing [[lst:configure-code-cells]]
configures =code-cells=.

#+caption[Configure =code-cells=]:
#+caption: Configure =code-cells=.
#+name: lst:configure-code-cells
#+begin_src emacs-lisp -n :results silent :tangle no
(when (ensure-package-installation 'code-cells)
  (with-eval-after-load 'code-cells
    (let ((map code-cells-mode-map))
      (keymap-set map "M-p" #'code-cells-backward-cell)
      (keymap-set map "M-n" #'code-cells-forward-cell)
      (keymap-set map "C-c C-c" #'code-cells-eval))))
#+end_src

*** [[https://stackoverflow.com/questions/2324758/debugging-python-programs-in-emacs][Debugging Python programs in Emacs]]
:PROPERTIES:
:CUSTOM_ID: sec:debug-python
:END:

[[https://github.com/realgud/realgud][RealGUD]] is the best option and in case of defaulting to {{{kbd(M-x pdb)}}}
debugging may work better with =tool-bar-mode= enabled.  Listing
[[lst:ensure-realgud]] ensures the installation of =realgud=.  Listing [[lst:pdb-numpy]]
is a debugging start by means of =pdb= or =realgud:pdb=.  Links of interest are:
- [[https://github.com/realgud/realgud][RealGUD]] provides a nice interface to PDB by means of {{{kbd(M-x
  realgud:pdb)}}} that also works well with =tool-bar-mode= disabled.
- [[https://realpython.com/python-debugging-pdb/][Python Debugging with PDB]]
- [[https://docs.python.org/3/library/pdb.html][The Python Debugger]]
- [[yt:vfPtGsSJldg][Introduction to PDB (Python-2.7 YouTube video)]]
- [[https://stackoverflow.com/questions/7668979/how-do-you-watch-a-variable-in-pdb][How do you watch a variable in PDB? (Python-2.7)]]
- [[https://stackoverflow.com/questions/51349074/in-python-3-7-does-the-opcode-event-from-sys-settrace-give-any-information-ab][How to use the opcode event (Python-3.7, GAV: why does it fail)?]]
- [[https://pypi.org/project/pdbpp/][PDB++]] looks incompatible with Python>3.10: see [[https://github.com/pdbpp/pdbpp/issues/516][Python-3.11 breaks PDBPP]].
- [[https://python-scientific-lecture-notes.developpez.com/tutoriel/notes-cours/python-debugging-code/#L3-1][Debugging Python with IPDB under IPython or with PDB in a terminal]].
- [[https://docs.spyder-ide.org/current/panes/debugging.html][Spyder Python debugging using IPDB]].
- [[https://docs.python.org/3/howto/gdb_helpers.html][Debugging C API extensions and CPython Internals with GDB]].  Making this work
  with =pyenv= is an unresolved issue: see [[https://github.com/pyenv/pyenv/issues/1190][Install python-gdb.py]].
Python info links of interest are:
- [[info:python#Debugging C API extensions and CPython Internals with GDB][Debugging C API extensions and CPython Internals with GDB (info)]].
- [[info:python#Debugging and Profiling][Debugging and Profiling (info)]].

#+caption[Ensure =realgud= installation]:
#+caption: Ensure =realgud= installation.
#+name: lst:ensure-realgud
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'realgud)
#+end_src

#+caption[PDB NumPy example: =python -m pdb .emacs.d/nuggy.py=]:
#+caption: PDB NumPy example: =python -m pdb .emacs.d/nuggy.py=.
#+name: lst:pdb-numpy
#+begin_src python -i -n :results silent
def buggy():
    from numpy import array, matrix
    from numpy.linalg import inv

    a = matrix(array([[1.0, 1.0], [1.0, 1.0]]))
    # Use "display", "p", or "pp" to inspect "a".
    # PDB: A series of "s" does not raise the exception here, contrary to "c".
    b = inv(a)
    return b

if __name__ == "__main__":
    b = buggy()
    # PDB: The series of "s" says only here "Uncaught exception".
#+end_src

* [[https://github.com/emacs-tw/awesome-emacs#library][Libraries]]
:PROPERTIES:
:CUSTOM_ID: sec:libraries
:END:

** [[info:dash.info#Top][Library dash.el (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:dash-library
:END:

The library [[info:dash.info#Top][dash.el (info)]] positions itself as a modern alternative for the list
processing API of [[info:cl#Top][cl]].  It is a requirement of important packages in this Emacs
setup (for instance [[https://github.com/andras-simonyi/citeproc-el#readme][citeproc]], [[https://github.com/magit/magit#readme][magit]], and [[https://github.com/Fuco1/smartparens#readme][smartparens]]).  Listing
[[lst:configure-dash]] enables fontification of =dash= macros and makes
=info-lookup-symbol= take into account the =dash= macros.

#+caption[Configure =dash= fontification and info lookup]:
#+caption: Configure =dash= fontification and info lookup.
#+name: lst:configure-dash
#+begin_src emacs-lisp -n :results silent
(when (fboundp #'global-dash-fontify-mode)
  (global-dash-fontify-mode))

(when (fboundp #'dash-register-info-lookup)
  (with-eval-after-load 'info-look
    (dash-register-info-lookup)))
#+end_src

** [[https://github.com/rejeep/f.el][Library f.el]]
:PROPERTIES:
:CUSTOM_ID: sec:f-library
:END:

The library [[https://github.com/rejeep/f.el][f.el]] positions itself as a modern API for working with files and
directories in Emacs.  It is a requirement of the [[https://github.com/andras-simonyi/citeproc-el#readme][citeproc]] package in this Emacs
setup and requires no configuration.

** [[https://github.com/magnars/s.el][Library s.el]]
:PROPERTIES:
:CUSTOM_ID: sec:s-library
:END:

The library [[https://github.com/magnars/s.el][s.el]] positions itself as the long lost Emacs string manipulation
library.  It is a requirement of the [[https://github.com/andras-simonyi/citeproc-el#readme][citeproc]] and [[https://github.com/bdarcus/citar#readme][citar]] packages in this Emacs
setup and requires no configuration.

* [[info:emacs#Minor Modes][Minor Modes (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:minor-modes
:END:

** [[https://github.com/victorhge/iedit#readme][Synchronal multiple-region editing]]
:PROPERTIES:
:CUSTOM_ID: sec:synchronal-multiple-region-editing
:END:

#+caption[Enable =iedit=]:
#+caption: Enable =iedit=.
#+name: lst:enable-iedit
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'iedit)
  (require 'iedit nil 'noerror))
#+end_src

** [[https://github.com/lewang/ws-butler#readme][Unobtrusive whitespace trimming]]
:PROPERTIES:
:CUSTOM_ID: sec:unobtrusive-whitespace-trimming
:END:

#+caption[Configure =ws-butler=]:
#+caption: Configure =ws-butler=.
#+name: lst:configure-ws-butler
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'ws-butler)
  (setopt ws-butler-keep-whitespace-before-point nil)
  (add-hook 'prog-mode-hook #'ws-butler-mode)
  (add-hook 'text-mode-hook #'ws-butler-mode))
#+end_src

** [[https://countvajhula.com/2021/09/25/the-animated-guide-to-symex/][Structural editing]]
:PROPERTIES:
:CUSTOM_ID: sec:structural-editing
:END:

Structural editing keeps character pairs (for instance parentheses, curly and
square brackets as well as single and double quotes) balanced to leave code (for
instance Lisp and Python) and text (for instance LaTeX and Org) structure
intact.  I use [[https://github.com/Fuco1/smartparens][smartparens]] which offers a normal mode (=smartparens-mode=) and a
strict mode (=smartparens-strict-mode=).  Although both modes insert character
pairs, the normal mode allows to delete one of the paired characters easily
while the strict mode does not.  Therefore, the strict mode is more for code
editing since it never breaks programming language rules and the normal mode is
more for text editing where structure is a matter of convention instead of
programming language rules.

For instance, the strict mode in Python allows to delete entire lists, tuples,
or the arguments after the cursor (what Emacs calls =point=) in a function call
without breaking the character pair balance.  In order to repair a broken
character pair balance, insert a single character by prefixing it with "C-q"
bound to =quoted-insert=.

The [[https://smartparens.readthedocs.io/en/latest/index.html][smartparens documentation]] targets experienced Emacs users.  The
following links show how to put the documentation to practical use:
1. The [[https://gist.github.com/pvik/8eb5755cc34da0226e3fc23a320a3c95][smartparens cheatsheet]] demonstrates its usage visually.
2. [[https://gist.github.com/oantolin][Omar Antolin's gist "my-smartparens-config.el"]] is the first place to look for
   how to tweak [[https://github.com/Fuco1/smartparens][smartparens]].  However, the gist may be partially obsolete, since
   it is not part of his current [[https://github.com/oantolin/emacs-config][Emacs configuration]].
3. [[https://lists.gnu.org/archive/html/help-gnu-emacs/2014-07/msg00135.html][How to enable smartparens in the minibuffer after eval-expression]] explains
   how the machinery after the first and after later usages of =eval-expression=
   differ and discusses options how to handle those differences.
Listing [[lst:setup-smartparens]] aims to setup [[https://github.com/Fuco1/smartparens][smartparens]] for Go, LaTeX, Lisp
dialects, Org, and Python.  Execute src_emacs-lisp[:results
none]{(sp-cheat-sheet)} for short documentation taking into account the
overridden key bindings in listing [[lst:setup-smartparens]].  Table
[[tab:smartparens-commands-and-bindings]] lists commands with key bindings taken in
order from src_emacs-lisp[:results none]{(sp-cheat-sheet)} that takes the
overrides of listing [[lst:setup-smartparens]] into account.  Finally, listing
[[lst:sp-eval-expression]] defines an alternative to =eval-expression= enabling
=smartparens-strict-mode= and =font-lock-mode=.

Despite the provocative post [[https://andreyorst.gitlab.io/posts/2022-02-20-what-if-structural-editing-was-a-mistake/]["What if structural editing was a mistake?"]],
[[https://github.com/Fuco1/smartparens][smartparens]] is one of my favorite packages. In particular, [[https://github.com/Fuco1/smartparens][smartparens]] handles
matching pairs in Org-mode files with export and source blocks for multiple
formats and languages almost (exceptions are due to ~Search failed~ errors
inside source blocks) correctly.  Therefore, [[https://smartparens.readthedocs.io/en/latest/index.html?highlight=show-smartparens-mode#getting-started][show-smartparens-mode]] highlights
matching pairs immediately in front or after point in such files correctly,
contrary to for instance [[https://github.com/Fanael/rainbow-delimiters#readme][rainbow-delimiters]].

#+caption[Setup =smartparens=]:
#+caption: Setup =smartparens=.
#+name: lst:setup-smartparens
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'smartparens)
  ;; GAV: Documentation says to require `smartparens-config'.
  (require 'smartparens-config)
  (setopt sp-base-key-bindings 'sp
          sp-override-key-bindings '(("C-(" . sp-backward-slurp-sexp)
                                     ("C-)" . sp-forward-slurp-sexp)
                                     ("C-M-(" . sp-backward-barf-sexp)
                                     ("C-M-)" . sp-forward-barf-sexp)))

  (add-hook 'conf-toml-mode-hook #'smartparens-mode)
  (add-hook 'prog-mode-hook      #'smartparens-mode)
  (add-hook 'text-mode-hook      #'smartparens-mode)

  (add-hook 'emacs-lisp-mode-hook      #'smartparens-strict-mode)
  (add-hook 'go-ts-mode-hook           #'smartparens-strict-mode)
  (add-hook 'ielm-mode-hook            #'smartparens-strict-mode)
  (add-hook 'inferior-python-mode-hook #'smartparens-strict-mode)
  (add-hook 'lisp-data-mode-hook       #'smartparens-strict-mode)
  (add-hook 'lisp-mode-hook            #'smartparens-strict-mode)
  (add-hook 'python-mode-hook          #'smartparens-strict-mode)
  (add-hook 'sly-mrepl-mode-hook       #'smartparens-strict-mode)

  (when (fboundp 'go-ts-mode)
    ;; Stolen from `smartparens-go':
    (sp-with-modes 'go-ts-mode
      (sp-local-pair "{" nil :post-handlers '(("||\n[i]" "RET")))
      (sp-local-pair "/*" "*/" :post-handlers '(("| " "SPC")
                                                ("* ||\n[i]" "RET"))))
    ;; Go has no sexp suffices.  This fixes slurping:
    ;; (|foo).bar -> (foo.bar)
    (add-to-list 'sp-sexp-suffix (list #'go-ts-mode 'regexp "")))

  ;; https://xenodium.com/emacs-smartparens-auto-indent/index.html
  (defun indent-between-pair (&rest _ignored)
    (newline)
    (indent-according-to-mode)
    (forward-line -1)
    (indent-according-to-mode))

  (dolist (left '("(" "[" "{"))
    (sp-local-pair 'prog-mode left
                   nil :post-handlers '((indent-between-pair "RET"))))

  (show-smartparens-global-mode +1))
#+end_src

#+attr_latex: :booktabs yes :float table
#+caption[Smartparens commands with key bindings in this setup]:
#+caption: Smartparens commands with key bindings in this setup.
#+name: tab:smartparens-commands-and-bindings
|--------------------------------+----------------------------+----------|
| command                        | keys                       | status   |
|--------------------------------+----------------------------+----------|
| sp-forward-sexp                | {{{kbd(C-M-f)}}}           |          |
| sp-backward-sexp               | {{{kbd(C-M-b)}}}           |          |
| sp-next-sexp                   | {{{kbd(C-M-n)}}}           |          |
| sp-prev-sexp                   | {{{kbd(C-M-p)}}}           |          |
| sp-down-sexp                   | {{{kbd(C-M-d)}}}           | shadowed |
| sp-backward-down-sexp          | {{{kbd(C-M-a)}}}           |          |
| sp-beginning-of-sexp           | {{{kbd(C-S-d)}}}           |          |
| sp-end-of-sexp                 | {{{kbd(C-S-a)}}}           |          |
| sp-up-sexp                     | {{{kbd(C-M-e)}}}           |          |
| sp-backward-up-sexp            | {{{kbd(C-M-u)}}}           |          |
| sp-kill-sexp                   | {{{kbd(C-M-k)}}}           |          |
| sp-copy-sexp                   | {{{kbd(C-M-w)}}}           |          |
| sp-forward-slurp-sexp          | {{{kbd(C-))}}}             | override |
| sp-backward-slurp-sexp         | {{{kbd(C-()}}}             | override |
| sp-forward-barf-sexp           | {{{kbd(C-M-))}}}           | override |
| sp-backward-barf-sexp          | {{{kbd(C-M-()}}}           | override |
| sp-forward-symbol              | {{{kbd(M-F)}}}             |          |
| sp-backward-symbol             | {{{kbd(M-B)}}}             |          |
| sp-unwrap-sexp                 | {{{kbd(M-<delete>)}}}      | shadowed |
| sp-backward-unwrap-sexp        | {{{kbd(M-<backspace>)}}}   |          |
| sp-splice-sexp                 | {{{kbd(M-D)}}}             |          |
| sp-splice-killing-backward     | {{{kbd(C-M-<backspace>)}}} |          |
| sp-splice-sexp-killing-forward | {{{kbd(C-M-<delete>)}}}    | shadowed |
| sp-select-next-thing           | {{{kbd(C-M-])}}}           |          |
| sp-select-next-thing-exchange  | {{{kbd(C-])}}}             |          |
| sp-mark-sexp                   | {{{kbd(C-M-SPC)}}}         |          |
|--------------------------------+----------------------------+----------|

#+caption[Define =sp-eval-expression= with =smartparens= support]:
#+caption: Define =sp-eval-expression= enabling =smartparens-strict-mode=
#+caption: and =font-lock-mode=.
#+name: lst:sp-eval-expression
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'smartparens
  ;; https://lists.gnu.org/archive/html/help-gnu-emacs/2014-07/msg00135.html
  ;; GAV: Reuse `read--expresssion-map' instead of defining my own map.
  (defun sp--read-expression (prompt &optional initial-contents)
    (let ((minibuffer-completing-symbol t))
      (minibuffer-with-setup-hook
          (lambda ()
            (emacs-lisp-mode) ; Enables `smartparens-strict-mode' too.
            (use-local-map read--expression-map)
            (font-lock-mode t))
        (read-from-minibuffer prompt initial-contents
                              read--expression-map nil
                              'read-expression-history))))

  (defun sp-eval-expression (expression &optional arg)
    "Evaluate EXPRESSION with `smartparens' support."
    (interactive (list (read (sp--read-expression "SP eval: "))
                       current-prefix-arg))
    (if arg
        (insert (pp-to-string (eval expression lexical-binding)))
      (pp-display-expression (eval expression lexical-binding)
                             "*SP Eval Output*")))

  ;; Do not change the "M-ESC :" `eval-expression' key binding.
  (keymap-global-set "M-:" #'sp-eval-expression))
#+end_src

** [[https://github.com/davidshepherd7/electric-operator#readme][Electric operators]]
:PROPERTIES:
:CUSTOM_ID: sec:electric-operators
:END:

Listing [[lst:configure-electric-operator]] configures =electric-operator-mode= to
add spaces around operators for compatibility with for instance the [[https://black.readthedocs.io/en/stable/][Black code
formatter for Python]].

#+caption[Configure =electric-operator=]:
#+caption: Configure =electric-operator=.
#+name: lst:configure-electric-operator
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'electric-operator)
  (add-hook 'c-mode-common-hook #'electric-operator-mode)
  (add-hook 'python-mode-hook   #'electric-operator-mode))
#+end_src

** [[https://joaotavora.github.io/yasnippet/][Smart snippets]]
:PROPERTIES:
:CUSTOM_ID: sec:smart-snippets
:END:

#+caption[Setup =yasnippet=]:
#+caption: Setup =yasnippet=.
#+name: lst:setup-yasnippet
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'yasnippet)
  ;; Set `yas-alias-to-yas/prefix-p' before loading `yasnippet'.
  (setopt yas-alias-to-yas/prefix-p nil)
  (add-hook 'LaTeX-mode-hook #'yas-minor-mode)
  (add-hook 'org-mode-hook #'yas-minor-mode)
  (add-hook 'python-mode-hook #'yas-minor-mode))
#+end_src

* [[info:emacs#Display][Display (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:display
:END:

** [[info:emacs#Narrowing][Narrowing]]
:PROPERTIES:
:CUSTOM_ID: sec:narrowing
:END:

Narrowing means focusing in on some portion of the buffer and widening means
focussing out on the whole buffer.  This allows to concentrate temporarily on
for instance a particular function or paragraph by removing clutter. The "Do
What I Mean" [[https://endlessparentheses.com/emacs-narrow-or-widen-dwim.html][narrow-or-widen-dwim]] function allows to toggle between narrowed and
widened buffer states.  Here, the function =narrow-or-widen-dwim= operates also
on any Org table, Org source block, Org block, or Org subtree.

#+caption[Configure =narrow-or-widen-dwim=]:
#+caption: Configure =narrow-or-widen-dwim=.
#+name: lst:configure-narrow-or-widen-dwim
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'emacs
  (declare-function org-at-table-p "org" (&optional table-type))

  (defun org-narrow-to-table ()
    "Narrow buffer to table at point."
    (interactive)
    (if (org-at-table-p)
        (narrow-to-region (org-table-begin) (org-table-end))
      (user-error "Not in a table")))

  (defun narrow-or-widen-dwim (p)
    "Widen a narrowed buffer, narrow \"Do What I Mean\" otherwise.
DWIM means: region, Org table, Org source block, Org block, Org
subtree, LaTeX environment, TeX group, or defun, whichever
applies first.  Narrowing to org-src-block actually calls
`org-edit-src-code'.

With prefix P, don't widen, just narrow even if buffer is already
narrowed."
    (declare (interactive-only t))
    (interactive "P")
    (cond ((and (buffer-narrowed-p) (not p))
           (widen))
          ((and (bound-and-true-p org-src-mode) (not p))
           (org-edit-src-exit))
          ((region-active-p)
           (narrow-to-region (region-beginning) (region-end)))
          ((derived-mode-p 'org-mode)
           (or (with-demoted-errors "DWIM: %S" (org-narrow-to-table) t)
               (with-demoted-errors "DWIM: %S" (org-edit-src-code) t)
               (with-demoted-errors "DWIM: %S" (org-narrow-to-block) t)
               (org-narrow-to-subtree)))
          ((derived-mode-p 'latex-mode)
           (LaTeX-narrow-to-environment))
          ((derived-mode-p 'tex-mode)
           (TeX-narrow-to-group))
          (t
           (narrow-to-defun))))

  (keymap-set ctl-x-map "n t" #'org-narrow-to-table)
  (keymap-set ctl-x-map "C-n" #'narrow-or-widen-dwim))
#+end_src

** [[https://jblevins.org/log/rainbow-mode][Visualize color codes and names]]
:PROPERTIES:
:CUSTOM_ID: sec:rainbow-mode
:END:

Listing [[lst:setup-rainbow-mode]] configures =rainbow-mode= to colorize color codes
and names in buffers for debugging.

#+caption[Setup =rainbow-mode=]:
#+caption: Setup =rainbow-mode=.
#+name: lst:setup-rainbow-mode
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'rainbow-mode)
  ;; GAV: Do not add `rainbow-mode' to any programming language hook,
  ;; since that interferes at least with Org export to LaTeX.
  (setopt rainbow-x-colors-major-mode-list
          (list 'c++-mode 'c-mode 'emacs-lisp-mode 'inferior-emacs-lisp-mode
                'lisp-interaction-mode 'org-mode 'python-mode)))
#+end_src

** [[https://karthinks.com/software/batteries-included-with-emacs/][Flash the line around point for visual feedback]]
:PROPERTIES:
:CUSTOM_ID: sec:flash-line-around-point
:END:

Listing [[lst:flash-line-around-point]] implements flashing of the line around point
for visual feedback after a selection of commands that make it hard to track
point movements visually.

#+caption[Implement =flash-line-around-point=]:
#+caption: Implement =flash-line-around-point=.
#+name: lst:flash-line-around-point
#+begin_src emacs-lisp -n :results silent
;; https://karthinks.com/software/batteries-included-with-emacs/
;; https://github.com/karthink/.emacs.d/blob/master/init.el#L2077
;; BUG#71537: Using `let' in `flash-line-around-point' implies
;; requiring `pulse'.
(require 'pulse)

(defun flash-line-around-point (&rest _)
  "Flash the line around point."
  (let ((pulse-iterations 16)
        (pulse-delay 0.1))
    (pulse-momentary-highlight-one-line (point))))

(advice-add 'scroll-up-command   :after #'flash-line-around-point)
(advice-add 'scroll-down-command :after #'flash-line-around-point)
(advice-add 'recenter-top-bottom :after #'flash-line-around-point)
(advice-add 'other-window        :after #'flash-line-around-point)
#+end_src

* Applications
:PROPERTIES:
:CUSTOM_ID: sec:applications
:END:

** [[info:emacs#Hyperlinking][Hyperlinking and Web Navigation Features (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:hyperlinking-web-navigating
:END:

*** [[info:emacs#Browse-URL][Browse URL (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:browse-url
:END:

Listing [[lst:configure-browse-url]] configures =browse-url=.

#+attr_latex: :options breaklines
#+caption[Configure =browse-url=]:
#+caption: Configure =browse-url=.
#+name: lst:configure-browse-url
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'browse-url
  (defun browse-url-mpv (url &optional _)
    (start-process "mpv" nil "mpv" url))

  (defconst browse-url-mpv-regexp
    (rx bos "http" (opt "s") "://"
        (or (seq "youtu.be/")
            (seq "www.youtube.com/" (or "embed/" "watch?"))
            (seq (+? nonl) (or ".mp4" ".webm") eos)))
    "Match hyperlinks to open with mpv.")

  (setopt
   browse-url-generic-program (or (when (eq system-type 'darwin) "open")
                                  (executable-find "firefox"))
   browse-url-handlers `((,browse-url-mpv-regexp . browse-url-mpv)
                         ("." . eww-browse-url))))
#+end_src

*** [[https://en.wikipedia.org/wiki/Eww_(web_browser)][Emacs Web Wowser]]
:PROPERTIES:
:CUSTOM_ID: sec:emacs-web-wowser
:END:

#+caption[Rename =eww= buffers and display =pdf= links properly]:
#+caption: Rename =eww= buffers and display =pdf= links properly.
#+name: lst:rename-eww-buffer-display-pdf-links
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'eww
  (defun eww-display-pdf-as-binary (fn &rest args)
    (let ((buffer-file-coding-system 'binary))
      (apply fn args)))

  (defun eww-rename-buffer ()
    "Rename the buffer using title or url."
    (let* ((title (plist-get eww-data :title))
           (name (or (and (eq "" title) (plist-get eww-data :url)) title)))
      (rename-buffer (format "*%s # eww*" name) t)))

  (add-hook 'eww-after-render-hook #'eww-rename-buffer)
  (advice-add 'eww-display-pdf :around #'eww-display-pdf-as-binary))
#+end_src

*** [[https://en.wikipedia.org/wiki/Media_type#Mailcap][Mailcap]]
:PROPERTIES:
:CUSTOM_ID: sec:mailcap
:END:

Extension packages as [[info:emacs#EWW][EWW (info)]], [[info:emacs#Gnus][Gnus (info)]], and [[info:org#Top][Org (info)]] rely on a [[https://en.wikipedia.org/wiki/Media_type#Mailcap][mailcap]]
file to know what application should open a specific media file type.  Listing
[[lst:tangle-mailcap-file]] specifies =emacsclient= as the application to open PDF
files.

#+caption[Tangle =mailcap= file]:
#+caption: Tangle =mailcap= file.
#+name: lst:tangle-mailcap-file
#+begin_src org -n :tangle ~/.mailcap
# https://emacs.stackexchange.com/a/24502 answers the question:
# How to use pdf-tools (pdf-view-mode) in emacs?
application/pdf; emacsclient %s
#+end_src

*** [[https://github.com/minad/osm#readme][Open Street Map viewer for Emacs]]
:PROPERTIES:
:CUSTOM_ID: sec:open-street-map
:END:

[[https://github.com/minad/osm#readme][Open Street Map]] is a tile-based map viewer with a responsive movable and
zoomable display and with a list of multiple preconfigured tile servers.
Listing [[lst:ensure-osm-installation]] ensures the installation of ~osm~ and
listing [[lst:using-osm-example]] is a minimal example of how to use ~osm~.  Inside
~osm-mode~ buffers, the key binding for the command
src_emacs-lisp{(osm-bookmark-set)} is {{{kbd(C-x r b)}}} allowing to bookmark
such buffers.  Outside ~osm-mode~ buffers, the key binding for the command
src_emacs-lisp{(call-interactively 'consult-bookmark)} is {{{kbd(C-x r b)}}}.

#+caption[Ensure "osm" installation]:
#+caption: Ensure ~osm~ installation.
#+name: lst:ensure-osm-installation
#+begin_src emacs-lisp -n :results silent
(ensure-package-installation 'osm)
#+end_src

#+caption[Using "osm" example]:
#+caption: Using ~osm~ example.
#+name: lst:using-osm-example
#+begin_src emacs-lisp -n :results silent :tangle no
(osm "Tower of London")
#+end_src

*** [[info:url#Top][URL (info)]]                                                     :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:url
:END:

[[https://lists.gnu.org/archive/html/emacs-devel/2024-03/msg00670.html][How to retrieve only URL metadata]]

#+caption[Make an URL HEAD request]:
#+caption: Make an URL HEAD request.
#+name: lst:url-head-request
#+header: :wrap "src text -n :eval no"
#+begin_src emacs-lisp -n :eval never-export :exports both :tangle no
(with-current-buffer
    (let ((url-request-method "HEAD"))
      (url-retrieve-synchronously "https://www.gnu.org/"))
  (buffer-string))
#+end_src

#+caption[URL HEAD request result]:
#+caption: URL HEAD request result.
#+name: lst:url-head-request-result
#+RESULTS: lst:url-head-request
#+begin_src text -n :eval no
HTTP/1.1 200 OK
Date: Wed, 27 Mar 2024 07:40:07 GMT
Server: Apache/2.4.29
Content-Location: home.html
Vary: negotiate,accept-language,Accept-Encoding
TCN: choice
Strict-Transport-Security: max-age=63072000
X-Frame-Options: sameorigin
X-Content-Type-Options: nosniff
Access-Control-Allow-Origin: (null)
Accept-Ranges: bytes
Cache-Control: max-age=0
Expires: Wed, 27 Mar 2024 07:40:07 GMT
Content-Length: 9803
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html
Content-Language: en

#+end_src

*** [[https://www.emacswiki.org/emacs/WebJump][Webjump]]
:PROPERTIES:
:CUSTOM_ID: sec:webjump
:END:

Listing [[lst:set-webjump-options]] binds {{{kbd(C-c j)}}} to =webjump= and
sets the =webjump-sites= option.

#+attr_latex: :options breaklines
#+caption[Set =webjump= options and bind the =webjump= command]:
#+caption: Set =webjump= options and bind the =webjump= command.
#+name: lst:set-webjump-options
#+begin_src emacs-lisp -n :results silent
(when (fboundp 'webjump)
  (keymap-global-set "C-c j" 'webjump)
  (with-eval-after-load 'webjump
    (setopt
     webjump-sites
     '(("CS 325 AI Programming" . "courses.cs.northwestern.edu/325")
       ("Emacs News" . "sachachua.com/blog/category/emacs-news")
       ("Mastering Emacs" . "www.masteringemacs.org")
       ("Planet Emacs Life" . "planet.emacslife.com")
       ("Worg - Org Mode Community" . "orgmode.org/worg")
       ("Git: Emacs" . "git.savannah.gnu.org/cgit/emacs.git")
       ("Git: Emacs MultiMedia System" .
        "https://git.savannah.gnu.org/cgit/emms.git")
       ("Git: GNU AUCTeX" . "git.savannah.gnu.org/cgit/auctex.git")
       ("Git: GNU ELPA" . "git.savannah.gnu.org/cgit/emacs/elpa.git")
       ("Git: NonGNU ELPA" . "git.savannah.gnu.org/cgit/emacs/nongnu.git")
       ("Git: Org Mode" . "git.savannah.gnu.org/cgit/emacs/org-mode.git")
       ("List: Org Mode" . "list.orgmode.org")
       ("List: Emacs Developer Archives" .
        "lists.gnu.org/archive/html/emacs-devel/")
       ("List: Help GNU Emacs Archives" .
        "lists.gnu.org/archive/html/help-gnu-emacs/")
       ("Counterpunch" . "www.counterpunch.org")
       ("Dictionary FR" . [simple-query "www.cnrtl.fr"
                                        "www.cnrtl.fr/definition/" ""])
       ("Dictionary NL" . [simple-query "www.woorden.org"
                                        "www.woorden.org/woord/" ""])))))
#+end_src

** [[info:gnus#Top][Reading News and Mail (info)]]                                    :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:reading-news-mail
:header-args:emacs-lisp: :tangle no
:END:

Reading news and mail:
1. [[https://www.maketecheasier.com/emacs-usenet-reader-with-gnus/][How to use Emacs as a USENET reader with Gnus]]
2. [[https://github.com/redguardtoo/mastering-emacs-in-one-year-guide/blob/master/gnus-guide-en.org][A practical guide to Gnus]]
3. [[https://jao.io/blog/2021-05-17-reading-and-searching-gmane-with-gnus-fast.html][Fast reading and searching of Gmane.io with Gnus]]
4. [[https://www.brautaset.org/posts/leafnode-nntp-os-x.html][Setting up Leafnode on macOS]]
5. [[https://blog.bitside.pl/posts/gnus/][Gnus]]
6. [[http://www.bobnewell.net/publish/35years/gmailhacks.html][Stupid GMail hacks for Gnus]]
7. [[http://www.bobnewell.net/publish/35years/gnuhacks.html][More stupid Gnus hacks]]
8. [[https://config.phundrak.com/emacs.html][See Mu4e section of Phundrak's Emacs configuration]]
Password management:
1. [[https://www.passwordstore.org/][Pass: the standard unix password manager]]
2. [[https://www.howtogeek.com/devops/how-to-use-pass-a-command-line-password-manager-for-linux-systems/][How to use Pass, a command-line password manager for Unix systems]]
3. [[https://vitalyparnas.com/guides/pass/][Clever uses of pass, the Unix password manager]]

#+attr_latex: :booktabs yes :float table
#+caption[Gnus key bindings]:
#+caption: Gnus key bindings.
#+name: tab:gnus-key-bindings
| command                        | map                 | keys           |
|--------------------------------+---------------------+----------------|
| gnus-group-list-active         | gnus-group-list-map | {{{kbd(A-A)}}} |
| gnus-group-list-all-groups     | gnus-group-mode-map | {{{kbd(L)}}}   |
| gnus-group-toggle-subscription | gnus-group-mode-map | {{{kbd(U)}}}   |
|--------------------------------+---------------------+----------------|

#+caption[Configure =gnus=]:
#+caption: Configure =gnus=.
#+name: lst:configure-gnus
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'gnus
  (setopt gnus-select-method '(nntp "news.gmane.io")))

(with-eval-after-load 'gnus-start
  (setopt gnus-check-bogus-newsgroups nil
          gnus-check-new-newsgroups 'ask-server
          gnus-read-newsrc-file t
          gnus-read-active-file 'some
          gnus-save-killed-list t
          gnus-save-newsrc-file t
          gnus-use-dribble-file t))

(with-eval-after-load 'gnus-sum
  (setopt gnus-thread-hide-subtree t))
#+end_src

** [[info:emacs#Sending Mail][Sending Mail (info)]]                                             :noexport:
:PROPERTIES:
:CUSTOM_ID: sec:sending-mail
:header-args:emacs-lisp: :tangle no
:END:

1. [[https://macowners.club/posts/email-emacs-mu4e-macos/][Email setup in Emacs with Mu4e on macOS]]
2. [[https://www.bounga.org/tips/2020/05/03/multiple-smtp-accounts-in-gnus-without-external-tools/][Setting up multiple IMAP and SMTP accounts in Gnus]]
3. [[https://jherrlin.github.io/posts/emacs-on-macos-monterey/][Emacs on Macos Monterey]]
4. [[https://github.com/00riddle00/dotfiles/blob/master/.msmtprc][Msmtp resource file for posteo.net]]
5. [[https://www.devdungeon.com/content/gpg-tutorial][GPG tutorial]]
6. [[https://en.wikipedia.org/wiki/Key_server_(cryptographic)#Keyserver_examples][Cryptographic key server examples]]
7. [[https://rakhim.org/fastmail-setup-with-emacs-mu4e-and-mbsync-on-macos/][Fastmail setup with Emacs, mu4e and mbsync on macOS]]

#+caption[Configure =message=]:
#+caption: Configure =message=.
#+name: lst:configure-message
#+begin_src emacs-lisp -n :results silent
(setopt user-full-name "Gerard Vermeulen"
        user-mail-address "gerard.vermeulen@posteo.net")
(with-eval-after-load 'message
  (setopt message-sendmail-envelope-from 'header))
#+end_src

#+caption[Configure =sendmail=]:
#+caption: Configure =sendmail=.
#+name: lst:configure-sendmail
#+begin_src emacs-lisp -n :results silent
(with-eval-after-load 'sendmail
  (setopt mail-specify-envelope-from t
          mail-envelope-from 'header
          send-mail-function #'sendmail-send-it
          sendmail-program (executable-find "msmtp")))
#+end_src

#+attr_latex: :options breaklines
#+caption[Resource file for =msmtp= on =Darwin=]:
#+caption: Resource file for =msmtp= on =Darwin=.
#+name: lst:darwin-msmpt-resource-file
#+header: :tangle (if (eq 'darwin system-type) "~/.msmtprc" "no")
#+begin_src conf -n
# Set default values for all accounts.
defaults
auth on
tls on
logfile ~/.msmtp.log

# CNRS on Darwin
# security add-generic-password -s cnrs -a gerard.vermeulen@neel.cnrs.fr -w
account cnrs
host smtps.grenoble.cnrs.fr
port 465
tls_starttls off
from gerard.vermeulen@neel.cnrs.fr
user gerard.vermeulen@neel.cnrs.fr
passwordeval security find-generic-password -s cnrs -w

# https://notmuchmail.org/emacstips/#index11h2
# https://wiki.debian.org/msmtp
# https://tushartyagi.com/blog/configure-mu4e-and-msmtp/
# https://www.emacswiki.org/emacs/GnusMSMTP
# https://www.ying-ish.com/essay/emacs-notmuch-mbsync-msmtp-email/

# Local Variables:
# mode: conf-unix
# End:
#+end_src

#+attr_latex: :options breaklines
#+caption[Resource file for =msmtp= on =Linux=]:
#+caption: Resource file for =msmtp= on =Linux=.
#+name: lst:linux-msmpt-resource-file
#+header: :tangle (if (eq 'gnu/linux system-type) "~/.msmtprc" "no")
#+begin_src conf -n
# Set default values for all accounts.
defaults
auth on
tls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
logfile ~/.msmtp.log

# CNRS on Linux
# secret-tool store --label=msmtp host smtps.grenoble.cnrs.fr service smtp user gerard.vermeulen@neel.cnrs.fr
account cnrs
host smtps.grenoble.cnrs.fr
port 465
tls_starttls off
from gerard.vermeulen@neel.cnrs.fr
user gerard.vermeulen@neel.cnrs.fr

# https://notmuchmail.org/emacstips/#index11h2
# https://wiki.debian.org/msmtp
# https://tushartyagi.com/blog/configure-mu4e-and-msmtp/
# https://www.emacswiki.org/emacs/GnusMSMTP
# https://www.ying-ish.com/essay/emacs-notmuch-mbsync-msmtp-email/

# Local Variables:
# mode: conf-unix
# End:
#+end_src

** [[https://github.com/skeeto/elfeed#readme][Elfeed: Emacs web feed reader]]
:PROPERTIES:
:CUSTOM_ID: sec:emacs-web-feed-reader
:END:

Listing [[lst:set-elfeed-options]] sets =elfeed= options, binds the =elfeed=
command, and makes a minimal attempt to enable =emms=.

#+caption[Set =elfeed= options and bind =elfeed= command]:
#+caption: Set =elfeed= options and bind =elfeed= command.
#+name: lst:set-elfeed-options
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'elfeed)
  (keymap-global-set "C-x w" #'elfeed)

  (with-eval-after-load 'elfeed
    (setopt
     elfeed-feeds
     '(("https://frame.work/fr/fr/blog.rss" framework)
       ("https://nullprogram.com/feed/" c-wellons)
       ("https://planet.emacslife.com/atom.xml" planet-emacs)
       ("https://protesilaos.com/codelog.xml" p-stavrou)
       ("https://sachachua.com/blog/category/emacs/feed" s-chua)
       ("https://updates.orgmode.org/feed/updates" org-updates)
       ("https://www.lemonde.fr/blog/huet/feed/" sciences))))

  (with-eval-after-load 'elfeed-show
    (when (fboundp 'emms-all)
      (emms-all))))
#+end_src

** [[info:emms#Top][Emacs Multimedia System (info)]]
:PROPERTIES:
:CUSTOM_ID: sec:emacs-multimedia-system
:END:

The link [[https://sqrtminusone.xyz/posts/2021-09-07-emms/][my emms and elfeed setup]] is a nice introduction to configuring and
using ~emms~ with ~elfeed~.  Listing [[lst:set-emms-options]] configures ~emms~
for ~mpv~ while eliminating use of ~mpd~.

#+caption[Set =emms= options]:
#+caption: Set =emms= options.
#+name: lst:set-emms-options
#+begin_src emacs-lisp -n :results silent
(when (ensure-package-installation 'emms)
  (with-eval-after-load 'emms
    (emms-all) ;; Restrict now to `emms-player-mpd' use only.
    (setopt emms-player-list '(emms-player-mpv)))
  (with-eval-after-load 'emms-mode-line
    (setopt emms-mode-line-format ""))
  (with-eval-after-load 'emms-player-mpv
    (setopt emms-player-mpv-update-metadata t
            emms-player-mpv-parameters
            (append emms-player-mpv-parameters
                    '("--ytdl-format=best" "--config=no" "--fullscreen"))))
  (with-eval-after-load 'emms-playing-time
    (setopt emms-playing-time-display-format " %s "))
  (with-eval-after-load 'emms-streams
    (setopt emms-streams-file
            (no-littering-expand-etc-file-name "emms/streams.emms"))))
#+end_src

* [[info:emacs#Init File][Init File (info)]] footer
:PROPERTIES:
:CUSTOM_ID: sec:user-init-file-footer
:END:

#+caption[Tangle the =user-init-file= footer]:
#+caption: Tangle the =user-init-file= footer.
#+name: lst:tangle-user-init-file-footer
#+begin_src emacs-lisp -n :results silent
(provide 'init)

;; Emacs looks for "Local variables:" after the last "newline-formfeed".

;; Local Variables:
;; indent-tabs-mode: nil
;; End:
;;; init.el ends here
#+end_src

* Local variables linking to [[#sec:latexmk-save-compile-display-loop][Latexmk save-compile-display-loop]]
:PROPERTIES:
:CUSTOM_ID: sec:local-variables
:END:

Only the [[info:org#Top][Org]] source file shows the local variables footer.

#+print_bibliography:

# Emacs looks for "Local variables:" after the last "newline-formfeed".

# Local Variables:
# bug-reference-mode: t
# compile-command: "latexmk -interaction=nonstopmode -lualatex -pvc -shell-escape README.tex"
# fill-column: 80
# org-edit-src-content-indentation: 0
# org-latex-src-block-backend: engraved
# eval: (org-eval-emacs-lisp-setup-blocks)
# End: